REF: Added exception handling to properties

also minor pylint cleanup
REF: Changed variable names in Energy, added exception handling
UPD: Docstring update for Energy

Minor change to Data docstring also
REF: Cleanup of the combine_data method

There is no purpose to setattr() for h,k,l, etc. now
REF: Rewrite of bg_estimate method

now takes a dictionary with type and value

Data docstring update
FIX: tolerances fixed after combine_data refactor