New ChColorAsset . If one object of this class is added to the asets of a body, all assets should get the specified color (it is up to the converters, ex for OpenGL or POV or Irlicht, to handle this behavior.)
If the ChColorAset is enclosed in a ChAssetLevel, only the shapes included in that level should get the color. This is similar to the behavior of ChTexture, btw., and it is very memory efficient.
Previously, one had to use a ChVisualization asset, but the name was misleading, and the confusing fact is that ChVisualization was also a base class of other shapes like spheres etc.
Some bugs in postprocesser and Irrlicht converter have been fixed too.
Old unused stuff removed.
Fixed the 'multiple defined symbols' linker issue that happened if you linked Irrlicht stuff  from more than one single .cpp. It did not happen with demos, in fact, that are single cpp, but in complex apps with Irrlicht viewing and more than one cpp, it caused troubles.
The problem was that ChIrrCamera and ChIrrEffects came from separate .h and .cpp files that I merged into single .h to keep things simple, but definitions were not inlined. Adding the 'inline' stuff fixed the problem.
Some changes in the FEM test code.