Create setting dialog

Created a setting dialog. and move theme, key binding menu to setting dialog.

Fixes : https://github.com/dart-lang/spark/issues/745

@ussuri @devoncarew @dinhviethoa

TEST=Manual

![image](https://f.cloud.github.com/assets/756988/1949473/5615bfa6-8109-11e3-9f7b-8a92f6bd05b9.png)

![image](https://f.cloud.github.com/assets/756988/1949472/2d7610f0-8109-11e3-8187-f496380ef3c5.png)