automatic import of orbit_mpi module only

Author: Juan F. Esteban Müller

py/orbit/core/__init__.py

@@ -1,15 +1 @@
-from . import aperture
-from . import bunch
-from . import collimator
-from . import error_base
-from . import field_sources
-from . import fieldtracker
-from . import foil
-from . import impedances
-from . import linac
 from . import orbit_mpi
-from . import rfcavities
-from . import spacecharge
-from . import teapot_base
-from . import trackerrk4
-from . import orbit_utils