add oxlibs

mrdna/readers/oxlibs/__init__.py

mrdna/readers/oxlibs/base.py

mrdna/readers/oxlibs/cadnano_utils.py

mrdna/readers/oxlibs/constants.py

mrdna/readers/oxlibs/pdb.py

mrdna/readers/oxlibs/pyquaternion/LICENSE.txt

mrdna/readers/oxlibs/pyquaternion/__init__.py

mrdna/readers/oxlibs/pyquaternion/quaternion.py

mrdna/readers/oxlibs/reader_lammps_init.py

mrdna/readers/oxlibs/readers.py

mrdna/readers/oxlibs/topology.py

mrdna/readers/oxlibs/utils.py