Experimental bite animation

Unity decided to reset project settings as well (thanks Unity)
Added settings saving (just difficulty for now)
Updated icon
Tongue animation changes to bite

Bite animation frames need to be updated to sync with the tongue.
Distance needs tweaking
Refactored eggs and frogs to use game clock events

Added EventIdentifiers to events
Also fix to events - RemoveAt(0) was removing the wrong event on
execution
Snake bite/tongue animations revised
Some tongue images not committed