Cleanup imports
Minor changes/fixes to ResourceManagerImpl.
* Changed from using "Double Brace Initialization" to a static map in the SoundEffectType enum.
* Unset the assetManager when the resource manager is disposed.
Minor cleanup changes to GameTouchController.
* Changed to constant values for the key codes.
* Changed specialAbilityListener to a list, as to allow for more listeners in the future.
Fixed imports and unused vars to fix most warnings.