Move shader program cache to CC3GLProgram.

Move shader program cache to CC3GLProgram. Add CC3GLProgramMatcher to facilitate
selecting an appropriate program for each node.
Minor fixes.

Add guard code to spherical bounding volume radius calc. Remove a redundant
method invocation on CC3Billboard.
Add several context-optimized GLSL shaders.

Add several context-optimized GLSL shaders, selected by program matchers.
Move program matchers to dedicated source file. Fix compiler crashes when
compiling GLSL illumination function with pre-iOS6 GLSL compilers. Add
resource loading timing logging facility.
Add ability to save POD files.

Add ability to save POD files. Add ability to save only the animation from a POD
file to a new POD file, and reload that POD into a node-hierarchy containing only
animation content. CC3PODResource now releases unneeded internal POD file
structures after loading and building.
Minor documentation & template changes.