Big commit, remember to divide in the future:
- Improved map culling with a more readable and faster algorithm (needs more testing);
- Restored debug drawing in neko and cpp;
- Restored correct sorting for all sprites;
- Fixed player sprite walk orientation;
- Simplified drawTilemap method a little;
- Updated FlxIsoTilemap to use the new drawTiles api names;
- Fixed FlxIsoSprite tile detection in adjustPosition  method;
- Added license file for ported Polygonal Labs sorting algorithms;
- Added Astar pathfinding algorithm, ported to Haxe and improved from the original as3 codeby Timo Virtanen (http://www.timovirtanen.com/);
- Added new spritesheet, courtesy of Telles0808 (http://telles0808.deviantart.com/art/RTP-Isometric-Games-151276404);
- Added filliping to sprites inside the map.