This update implements reading from text files to create levels.

To create a new level, simply create a method calling the “createLevel”
function with the input of the world and the names of the text files
you are loading for the textures and the functions of the blocks;
everything else with be automatically dealt with by the new method in
MapData. (I wanted to move it into TileMap to keep overarching code
together in one spot, but difficulties involving infinite pieces of
data being constructed prevented that from happening)
Merge branch 'master' of https://github.com/Sigma-Delta-Blah/PlatformerJoy