Various fixes to flash.geom package.

Added missing methods for Point, Rectangle, Matrix, Matrix3D and Vector3D. Reformatted some toStrings().

Biggest two alterations are the addition of Matrix3D.pointAt using the implementation found in openfl-html5, and the removal of inline keyword from the majority of Matrix3D methods. Normally I'd inline everything just like that but no methods on the other geom classes are inlined, and we need some better performance benchmarks before we can make such calls, I feel.