fix haxelib package
move DisplayObjectTween to flash lib
minor
relocate sources to src again (improved haxelib3 git/dev support)
move Sprintf to separate haxelib library (polygonal-sprintf, de.polygonal.Sprintf)
use single quotes for string interpolation only
Sprintf -> Printf
also print predicate expr in assert (useful if no info string was passed)
unify toString of vector and matrix classes
use haxe.ds.Vector
free after unregistering Entity
update README
Merge branch 'dev' of github.com:polygonal/core into dev

Conflicts:
	haxelib.json