This is a lot easier to manage than having them in the code.
For now it piggybacks on the map hack feature, later this should use the same scripted approach as GZDoom.
The duplicate 'currentSprite' variable prevented it from doing anything.
Also cleaned up the interface a bit to avoid using a global variable for parameter passing.
Fixes#279
This unexpectedly turned out a complete rewrite so now it is under my own license.
Also moved the remaining parts of map hack loading into the engine.
Overall I have to say that the feature is not what I expected, it's merely used to fudge the positioning of model sprites and for adding Polymer lights.
