Bugfixes galore

• Update to libdot 1.19. Bug fixes.
• Update to hterm 1.73. Various bugfixes and minor features.
• crosh: Fix pasting Unicode content.
• Fix base64url encoding translation with relays.
• Display relay error messages to the user.
• Detect relay loops.
• agent: Print SSH public key blobs to the console.
• Add a guide for setting up smart card backed ssh keys.
• agent: Improve TLV handling with smart cards.
• agent: Take OpenPGP card capabilities into account.
• agent: Add short names for Gemalto readers.
• Validate relay options.
• Ignore common browser shortcuts in connection dialog.
• omnibox: Allow matching saved profile names.