Harmonize CMB mesh server launcher with SMTK path helpers.

[vibraphone]

Paths in smtk/bridge/discrete/extension/meshing/vtkCMBMeshServerLauncher.{h,cxx} should be added to smtk/common/Paths.{h,cxx} (via the OS-specific helper classes). Then the vtkCMBMeshServerLauncher should use Paths.