Adding hotkeys for authoring Touch UI. Fixes #248.

Added support for hotkeys in touch ui. 

ctrl+shift+e for edit layer
ctrl+shift+p for preview layer
ctrl+shift+a for annotate layer
ctrl+shift+d for developer layer
ctrl+shift+t for targeting layer
ctrl+shift+s to toggle sidepanel
I think these hotkeys are unobtrusive enough that we are safe enabling them all the time like this. Of course a more elaborate solution would be to let each user enable/disable and set their own key bindings, but I think that's probably a bit much at this point. I'm inclined to merge this and put it in the next release. My guess is that no one who isn't looking for the key bindings will never know they exist.