Merge pull request #3 from Zemledelec/master

Multitexturing overlays. Maximum overlays is 8. Check shader's varyings.
Merge branch 'master' of https://github.com/OpenGlobus/OpenGlobus
Reduce visual quality: Increase camera view angle, change back real heights factor, decrease lod node factor.
Added two types to the shader program: int array, float array.
Added two layer options: opacity and transparent color.
Added overlays variables opacity and transparent color. Replace varying array to the fragment shader's uniform.