Reconcilliation (#895)

* Resolve fitting duplication

* resolve duplicate HEDM instrument code

* Remove unnecessary `simlp` variables causing confusion.

* Move hexrd/core/fitting/calibration/grain.py to HEDM

* Move hexrd/core/fitting/grains.py to HEDM

* Move GenerateEtaOmeMaps to HEDM

* Move fitting __init__.py file.

* Update imports

Author: ZackAttack614

hexrd/core/fitting/calibration/__init__.py

@@ -3,14 +3,12 @@
 from .lmfit_param_handling import fix_detector_y
 from .powder import PowderCalibrator
 from .structureless import StructurelessCalibrator
-from .grain import GrainCalibrator
 
 # For backward-compatibility, since it used to be named this:
 StructureLessCalibrator = StructurelessCalibrator
 
 __all__ = [
     'fix_detector_y',
-    'GrainCalibrator',
     'InstrumentCalibrator',
     'LaueCalibrator',
     'PowderCalibrator',