Rename sponza example & create directory for test models

Test resources are not placed in repo
Remove printf from model.cpp
Whitespace fix
Input: Change to a more standard control scheme
Move depth shader to post directory
Add a example testing depth buffer
Remove debug printf
rendertarget: use float instead of byte for depth
rendertarget: explicitly using INTENSITY instead of implicit LUMINANCE
rendertarget: disable GL_COMPARE_R_TO_TEXTURE

This breaks shadowmaps but fixes rendering depth. Need to find a proper solution.
rendertarget: use separate samplers for depth.

Depending on what the depthmap is used for it needs different parameters, e.g. shadowmapping requires GL_COMPARE_R_TO_TEXTURE but plain access cannot use it.
shaders: linear_depth takes uv instead of using screenspace.
Merge pull request #62 from ext/misc20131222

Misc fixes