Add config file (detector config dicts) and include in Base class

enerfit, fwhmfit, mca_cal, shape_cal
Add SpectrumExporter class to model; migrate write_spec functionality

Incomplete class that's not ready for running. Cleaning up
functionality that's been migrated from write_spec, now a method for
the Exporter class. Attention needs to be paid to how the output stings
are constructed and writtten to the file. The 'times' dictionary has
also undergone changes that need to be addressed in class methods.
Add placeholder instance of Exporter class to view; change comparisons to idiomatic Python