Add backspace to emoji drawer (+ two tiny tweaks)

Thought this would be useful, and someone was even generous enough to leave unused drawables for the purpose:

![Screenshot](https://cloud.githubusercontent.com/assets/124223/3757758/0d3b21ec-183d-11e4-9774-7b06a061076b.png)

Also two other small tweaks. (I personally think it's better without the gray placeholder squares, but that's just my opinion, man.)
super obsessive compulsive, but can we move this statement to the bottom of the method so the assignments all happen in a row? It's how the format is in our other `initializeResources()` methods.