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.)
only one instance is created so it's essentially static already, i say let it be but moved to the top of class for readability