Build improvements, i18n helpers, and npm support

• mkzip: trim empty directories.
• build: push shflags usage to leaf scripts.
• readlink: convert to python.
• get_relative_path: convert to python.
• pylint: new helper.
• concat: convert to a python script.
• build: start a common libdot.py module.
• build: disable node download logic for crosh builds for now.
• build: add support for using npm in builds.
• stack: rewrite and add tests.
• MessageManager: prefer browser translations over local ones.
• i18n: move getMessage helper here.
• i18n: move replaceReferences helper here.
• i18n: start a new file to hold i18n/l10n related funcs.
• plugin-to-platform-specific: delete unused vars.

A11y improvements, and keyboard/mouse tweaks

• Update to libdot 1.23. Build improvements, i18n helpers, and npm support.
• mouse: Support horizontal mouse scroll wheel events.
• keyboard: Add more keyboard binding callbacks.
• mouse: Disable default handling for mouse buttons 3 & 4.
• keyboard: Ignore Tab keys in onKeyPress_.
• etc: osc52.el: Fix terminal detection.
• build: mkdist: Delete dead code.
• a11y: Ensure the Page Up button isn't shown when the ScrollPort is focussed.
• build: Convert concat to a python script.
• a11y: Only announce a space character if it is the character actually printed to the screen.
• a11y: Mark offscreen rows that hold selection as hidden.
• a11y: Update the selection when accessibility is enabled even if it's collapsed.
• test: Remove invalid page-down-all-rows-visible test.
• a11y: Add announcements of the Space character.
• a11y: Handle announcements of selection changes.
• a11y: Simplify handling of duplicate live output.
• a11y: Change to have a role="log".
• a11y: Announce messages shown by showOverlay.
• a11y: Fix announcement of current scrolled percentage.
• a11y: Don't announce page up/down at the top/bottom of the screen.
• a11y: Fix an assertion failure in hterm.AccessibilityReader.
• test: Add simple test page.
• test: Add/update various test data files.
• a11y: Make it possible to enable/disable accessibility at runtime.
• a11y: Announce the current screen content on Page up/down.
• a11y: Add skip-links to allow screen readers to scroll the terminal.

Extension startup fix

• Update to hterm 1.80. Minor tweaks.
• prefs: Support translating hterm categories.
• Automatically add -oSendEnv args for hterm env vars.
• Fix a11y crash in extension on non-CrOS systems.
• FAQ: Document mouse cursor customization.

Minor tweaks

• prefs: Add COLORTERM to default env.
• vt: Automatically hide the mouse cursor while typing.
• vt: Improve & document mouse cursor customization.

OpenSSH 7.7p1, Unicode 11.0.0, and bug fixes

• Update to libdot 1.22. Unicode 11.0.0 updates and new helpers.
• Update to hterm 1.79. A11y (screen reader) improvements & keyboard/mouse fixes.
• crosh: Extend for arbitrary commands.
• crosh: Support passing command line args down.
• sftp: Fix directory deletion and copying.
• docs: Improve building/reference documentation.
• extension: Add a link to the options page at the bottom.
• Use new lib.f.lastError helper.
• crosh: Display errors from terminalPrivate if available.
• removeFile: Fix param typo.
• docs: Update the hex ids info.
• terminal: Adds the crostini terminal icon to use with crosh.
• ssh_client: Update to openssh-7.7p1.
• FAQ: Add a X11 forwarding answer.
• FAQ: Add omnibox with multiple extensions.
• API: Add onSendMessageExternal to allow FilesApp to sftp mount.
• lint: Clean up semi-colon usage.
• a11y: Add basic support for announcing command output to AT.
• Handle option page loading failures.
• docs: Document the crosh code on the Chrome side.
• gsc: Implement a PIN cache for GSC agent.
• a11y: Preserve selection when scrolling collapsed selections.
• crosh: Pass the selected profile over.
• ssh_client: Stub out permission check.
• agent: Improve gnubby extension probing.
• Crush all images.
• release: Automatically minimize translations.
• ssh_client: Add a echosshd utility.
• l10n: Improve pref descriptions and translation tips.
• l10n: Import updated translations.
• prefs: Auto-select icon for preferences page.

Unicode 11.0.0 updates and new helpers

• Start a dedicated README file.
• lint: Add some linting script helpers.
• concat: Improve handling of escapes with string embedding.
• lib.f.lastError: New helper.
• readlink: Fix python-3 print func handling.
• lib.CredentialCache: New cache helper.
• wcwidth: Update lookup tables to Unicode 11.0.0.
• imgcrush: New helper script for crushing images.
• mkzip: Automatically minimize translations.

A11y (screen reader) improvements & keyboard/mouse fixes

• Update to libdot 1.22. Unicode 11.0.0 updates and new helpers.
• osc52.vim: Split base64 output when using get_OSC52_DCS for screen.
• keyboard: Add media key handling only for Chrome OS systems.
• keyboard: Cleanly handle Firefox keyboard deviations.
• keyboard: Update Chromebook media bindings.
• build: Fix base64 usage on macOS.
• vt: Strip most control chars out for bracketed paste.
• keyboard: Improve addKeyDef documentation.
• mouse: Don't use user-configured word break matches when ctrl-clicking on urls.
• mouse: Double click should expand selection whether "copy-on-select" is on or off.
• a11y: Hide invisible elements from the screen reader.
• a11y: Add the aria-readonly attribute to the x-screen element.
• vt: Fix initial cursor display to match internal state.
• vtscope: Fix python-3 print func handling.
• prefs: Add Noto Sans Mono to the default font list.
• Clean up code a bit to pass linting.
• a11y: Add basic support for announcing command output to AT in hterm.
• a11y: Improve accessibility command output.
• tests: Add callbacks with image loading.
• terminal: Preserve selection when scrolling collapsed selections.
• Crush all images.
• tests: Fix floating point rounding error in Terminal.dimensions.
• vt: Unbreak legacy mouse wheel encoding.
• vt: Implement OSC 104 (color reset) support.
• vt: DECALN: Fix cursor position.
• prefs: Improve descriptions and translation tips.

Few new features and support for Chrome Extensions

• Update to hterm 1.78. Extended underlying support.
• Rework label alignment logic.
• Accept URI escapes in usernames & fingerprints.
• Document extensions that whitelist us.
• sftp: document the source a bit more
• Delay some connection dialog work until visibility.
• Unify params object setup.
• Document expected coding style.
• Support running as an extension.

Extended underlying support

• Add support for changing underline style/color.
• README: document our mirrors/release sites.
• Fix typo in autocapitalize attribute.
• Send a signal when the frame is made visible.
• Document expected coding style.
• Fix fallback git value.

Bug fixes & smaller extension downloads

• Update to libdot 1.21. Minor fixes.
• Update to hterm 1.77. Various bug fixes.
• Remove screenshots from releases.
• Document F11 when running in a tab for fullscreen for keyboard shortcuts.
• Shuffle nacl plugin paths for CWS filtering for smaller downloads for users.
• Fix resize errors after connect.
• Fix minor dialog error w/unbalanced rows.
• Set charset=utf-8 in html files.
• Refactor URI parsing into helper functions.
• Parse out fingerprint from ssh:// URIs.