Support more ways to build with dependency to collada-dom library (Debian/Ubuntu/Others)

[psi29a]

1. Add more paths to find collada library. Existing onces ignore the default install location defined here.
2. Find collada dependencies only when found static library. If it's only dynamic library, all dependencies are linked to it and there is no need to find them. Attempt to do so may fail because of locations mismatch. CMakeModules/FindCOLLADA.cmake supports only very specific locations for them.

A similar one is done here: pull request

Note: I've already been carrying these fixes on Debian and Ubuntu as well in our static builds for OpenMW. Others also make use of the patch to work around the issue of how the collada-dom is included. It would be great to have this in OpenSceneGraph-3.6