Refactored mirscanCriteria out of mirscanModule

All classes and functions pertaining to the hairpin criteria features have been
refactored from mirscanModule.py to mirscanCriteria.py. These functions are only
relevant to criteria features and criteria features do not call any of the
remaining functions of mirscanModule.py.

All executable scripts and mirscanModule.py have proper docstring documentation
and sane variable names. Only the functions related to criteria features must
still be cleaned up.