Adding a basic rule-based terrain painting implementation.

http://www.garagegames.com/community/resources/view/17145
Merge pull request #272 from thecelloman/kpaint

Adding a basic rule-based terrain painting implementation.
Filling out the variable names in the function prototype for autoMaterialLayers() for clarity.
Minor whitespace formatting changes (spacing) for consistency.
Merge pull request #273 from thecelloman/kpaint-addendum

Filled in the variable names in autoMaterialLayers() prototype