CMake Cleanup

Created by: anjos

This ticket keeps track of needed CMake script updates to tackle the following:

1. Clean-up the PCH support by removing this
2. Find a way to keep the "package" support, but do not depend on the "install" directory to find headers. This tends to work badly with template files and in other special cases.
3. Maybe port Cmake stuff to Scons?
4. Try other build systems?