Revert "rename texData.tex_coords"

This reverts commit 2182760b6c82cd1536c4a20660f23bb22d20211b.
update setCompression doxy

adds warning: not yet implemented
implement [dis|en]ableMipmap() syntax

+ follows @ofTheo's suggestion in making the mipmap syntax more straightforward:

+ call mTex.enableMipmap() before you load a texture to auto-generate mipmaps and automatically set the min-filtering for this texture to the OpenGL default, GL_LINEAR_MIPMAP_LINEAR.

 + doxy now notes side-effect minFilter state change.

+ polish syntax to use singular for mipmap, since one mipmap is generated per texture, also follows OpenGL API