INPUTMANAGER: Binding support

-Added small buffer to falldeath bounds
-Heavily modified inputmanager:
–key_map is now a dictionary of String→PseudoKey
—Removed name_map
—Added functions to PseudoKey variables
–Added binding check
—Pulls bindings from PlayerPrefs (String→int)
—Writes missing bindings to PlayerPrefs
–Instead of using “none”, use null
-Small cleanup to MobileGUI

TODO:
-Rebind keys in options menu