Add support for KTX / ZKTX file format
Created CubemapData, revert to typed CubemapAttribute, adapted Cubemap,
KTXTextureData and tests
Merge branch 'master' of https://github.com/vbousquet/libgdx into PR2431
Xoppa comments + Completed 'managed' support + ShaderCollectionTest
clean up
TextureData factory in GLTexture + FacedCubeMap face changes + test
Cleaned-up TextureData instiation (static Factory class)
Made methods name consistent in TextureData
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'upstream/master'

Conflicts:
	gdx/src/com/badlogic/gdx/graphics/GLTexture.java
Cleanup previous commit (setting file was wrongly comitted)
Merge branch 'master' of https://github.com/vbousquet/libgdx into PR2431
Merge branch 'master' of https://github.com/libgdx/libgdx into PR2431
Need to specify a precision
Merge branch 'master' of https://github.com/libgdx/libgdx into PR2431
Update CHANGES for KTX/ZKTX support