WIP: Add labels for email conversations
A label corresponds to an IMAP folder. Some filtering should probably be done to hide some standard/uninteresting IMAP folders from the labels view.
I've shamelessly stolen the drawing code from count-badge.vala, and I am using the coloring code from Util.Avatar. Perhaps the Util.Avatar code should be moved to a more general util file, given that it can be used for coloring various things..
I think some spacing (especially above the labels) could make it look a bit nicer. The label colors is also perhaps a bit sharp. Perhaps some alpha could be applied to make them blend in a bit better.
Here's how it looks right now:
This (at least partially) solves #83.