Mythbuntu theme modifications pre-0.27 release

As usual all commits are annotated. Highlights:

+ Channel icons are created on the fly in the Guide Grid and OSD if real icons aren't available, to avoid ugly blank spots.
+ No more ugly colored balls on Upcoming Recordings and other program list windows. Instead, use colored text.
+ Shrink OSD slightly.
+ Add Ubuntu font files so non-Ubuntu users will have them without needing manual installation.

My modifications to recordings-ui.xml are not included as they are based on the version prior to your recent major changes

fbe3dd29b1fcbf25dbc0c3beb8d41328aac3d927 031ff312df42955cb4579f4291889691037e5afd e2862583763a9e5630e627584bafe3168e2be40d

I would prefer to wait until you undo them so you can better see my changes. Let me know if you want me to commit it anyway.