BUG: _foamAddPath not available when foamPV alias/function is used

STYLE: only use paraview settings when actually available

- this means executing makeParaView prior to building OpenFOAM itself,
  but is consistent with the instructions given by makeParaView,
  and elminates anticipating the source location from the paraview
  config file, which increases the build flexibilty for ThirdParty