pre-sftp

• Rebuilt plugin again for working agent.
• Initial sftp work for Chrome OS. Not enabled in manifest.
• Improve exit cleanup logic.

relay fixes

• Fix some logic bugs in stream reworking.

hterm 1.61 + sftp prep

• Bump min Chrome version to 41 since we don't test on anything older.
• Rebuilt ssh_client plugins to include some fd related changes.
• Update to hterm 1.61. Fixes missing last line, and adds clickable URLs.
• Include ssh man pages in html form for users to read.
• Fix --proxy-port passing for Google relays.
• Add Ctrl-Shift-P shortcut in crosh for opening preferences.
• Drop blocking of Ctrl-Shift-N shortcut in crosh.

A little polish

• On ctrl-click, if a URL is selected, launch a new tab with the URL.
• Update test lists to match all the existing ones.
• Polish documentation/comments.
• Fix missing last line with some fonts/zoom levels.
• Allow keyboard shortcuts to be more easily bound by users.

hterm 1.60

• Update to hterm 1.60. This horizontal cursor position tracking.

Full bake

• Fix horizontal cursor tracking broken by the misrendering fix.

hterm 1.59

• Update to hterm 1.59. This fixes loading errors under Chrome M54+.

A little polish

• Fix hexToRGB parsing of more formats.
• Fix misrendering of last line with some resolutions.
• Update window.postMessage API to work with Chrome M54+.

copySelectionToClipboard fixes

• In hterm_terminal.js, use Terminal.prototype.copySelectionToClipboard, rather
  than the raw hterm.copySelectionToClipboard.

hterm 1.57, minor polish

• Update to hterm 1.57.
• Update various short URLs.
• Try to fix blank page on startup problems.