Created two new frame order system tests for the free rotor isotropic cone PDB representation file.
This is the two PDB files from the frame_order.pdb_model user function. The two new system tests
are Frame_order.test_pdb_model_iso_cone_free_rotor_z_axis and
Frame_order.test_pdb_model_iso_cone_free_rotor_xz_plane_tilt.
