Merge pull request #1 from MasDennis/master

master merge
Adds alpha masking parameter to AMaterial

Also updates corresponding shaders to include new preprocessor
directives and related condition handling
Added "threshold" uniform

Alpha mask threshold is now adjustable via
`AMaterial.setAlphaMaskingThreshold()` -- javadoc added
Housekeeping

Syntax cleanup requested by @jayschwa
Added more javadoc
Housekeeping
Merge pull request #598 from Davhed/smart-masking

Super simple alpha masking