BUG #14827: Fix ParaView module requirements.

+ Added a new option to enable/disable command line tools when Qt GUI is
not being built.
+ When command line tools are being built, ensure that the
vtkPVServerManagerApplication module is enabled.
+ Cleaned up how ParaView's CMakeLists.txt requests for modules based on
user settings. Using the _REQUEST_BY mechanism rather than forcing a
cmake cache variables ensures that when the Cmake cache variables act in
the same as module requesting other modules -- thus enabling
configurations where PARAVIEW_BUILD_QT_GUI is OFF, but pqCore module is
explicitly enabled by the user, etc.

Change-Id: I357e6250c766fd7c3488a1307c9063eddebd6e17
Merge topic '14827_fix_paraview_module_requirements' into next

6c73de6f BUG #14827: Fix ParaView module requirements.