Flipped, rotated and animated tiles for FlxTilemapExt

Hi, I've been working on updating FlxTilemapExt to get flipped, rotated and animated tiles.

It's my first time with Haxe and HaxeFlixel so I don't know if it's the best solution but, right now, it works. If you find something wrong or anything weird, let me know.

Btw, it also add support to get if the tile is flipped or rotated for tmx maps made with Tiled Editor, but only with the base64 encoding. I can't get it working with the csv encoding because it needs an unsigned int and I can't find a function to convert a string to an uint :/