Setup

This implements Allan Day's mockups for our new preferences dialog.

It looks great:
![screenshot from 2013-12-08 11 37 46](https://f.cloud.github.com/assets/272170/1699706/278d036c-5fba-11e3-97ed-7f12e09c597d.png)

The pull request also includes two tiny fixes for stupid mistakes I made when porting the settings from IBusConfig to GSettings. Oops!