ApplicationMain OpenFL 2.1.5 compatibility

(NMEPreloader is no longer the default PRELOADER_NAME for some reason).
Implemented own DefaultAssetLibrary (2.1.5 compat).

"Fun". A lot shorter though.
Eliminated some function($this) cases in output.

Weird Code Elimination?
Rewrote and reformatted Assets.get*

... -300 LOC?? I wonder if I missed anything.
Rewrote and reformatted the rest of Assets.
I guess that's a new version.
Moved Lib.mobile into a method to help DCE.
Experimental interfaces for commonly unused cases

Not every application uses images. Even fewer applications use binary
assets. This set of changes helps DCE exclude classes entirely unless
they are actually used. Interesting stuff.