Functioning keyboard layout

Keyboard layout now working, including mostly working MathConstantView.

Current issues: 
The View does not allow scrolling or zooming, so any constant too big for the screen falls off.
The buttons for pi and e should recolor when selected, but they do not do this yet.
The "Enter" button has no onClick
The "Delete" button really is more of a backspace, icon for that should be placed instead.