Test more build configurations
Our buildbots currently test configurations that have most of the bells+whistles enabled. We should add 2 more builds:
- minimal sessions: disable all modeling sessions but include all of the extensions such as Qt, ParaView, OpenCV, etc.
- minimal extensions: disable all extensions, but include as many modeling sessions as possible (polygon, mesh, vtk, discrete, oscillator, rgg, ...).
The former ensures applications targeted to 1 or a small number of modeling sessions will not have problems with dependencies introduced by extensions on modeling sessions. The latter ensures that dependencies on extensions don't accidentally creep into modeling sessions (i.e., if there are cross-dependencies they should be in separate libraries that are conditionally compiled).