Adding SBML validation scripts

This set includes the core C++ script that uses libsbml (trns_validate_SBML.cpp), and from which all stdout and stderr originates. It's designed to print out error messages if they arise, but they'll be in libsbml format.

There's a python wrapper that I copied from the GBK version, if needed, a binary that I compiled with libsbml v 5.10.2 in kbase-image-v26, and a test sbml file (that has zero errors, one can attempt to break it and see what the validation says)