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
Removed typo at the end of the shader

There was `";\n` at the end of the shader which probably got left over from when it was copied in from a static String.
Fixed a bug with backsided objects.

Front face vertex winding for backsided objects were incorrectly set to clockwise winding.
Remove texture on destroy

Addressing the bug which causes number of textures to increase at every reload as reported in Issue #528.