Changes

Minor improvements and fixes. (#1253)

  - Use the CMake variable OPENMODELICA_NEW_CMAKE_BUILD to signify that
    OMSimulator is being built as part of the OpenModelica CMake project.
    This was represented by the variable OPENMODELICA_SUPERPROJECT. However,
    as it turns out there is no need to add a new variable. It is also
    more descriptive because what we really want to know is that it is part
    of the OpenModelica CMake build and not just part of OpenModelica (as
    in the autoconf build).

  - Install `src/OMSimulatorServer/OMSimulatorServer.py` all the time. While
    it can be done only when part of OpenModelica, it creates unnecessary
    complication in that we will now need an additional variable to tell
    us if OMSimulator is part of OpenModelica but being used by the autoconf
    build instead of the CMake one.