- Update version numbers and documentation
- Fix github releases oauth key

Colors are generated asynchronously now and the TimelineItem is
updated when the color generation finishes.  This allows the UI
to stay responsive while new colors are being generated.

Preparing for 0.6.3 release

escape id when joining a room

When opening images in the full-screen overlay, there is now
a download button next to the close button.  This button utilizes
the same functionality as the right-click->save image button.

Restored the emoji picker, but it now falls back to the system
instead of forcing Emoji One.  The allows users to user the
picker for convenience, but doesn't enforce the emoji style on them.

This reverts commit 4b807229.

Add initial loading of qt jdenticon plugin:
https://github.com/redsky17/qt-jdenticon

Currently, the library's functionality has not been integrated
into the rest of nheko.  Next step is to add a configuration
item in the User Settings and use the plugin to generate
avatars for users without their own picture.  These avatars
should be cached in the Cache object.

User colors are now stored in cache.  This is consistent
with other similar variables.  I think there's a bug
right now where it doesn't properly refresh colors
for the TimeLineItem when the theme is changed.

When user is mentioned (via matrix 'highlight_count'), inactive
rooms will use a different color for the notification circle than
when only general unread messages exist.