Report energy_correction in __repr__ of a Configuration.

This could help when reporting Configuration objects,
and at least makes debugging less misleading.
Without this offset, all your energies are wrong.
See #2791.
But this alone doesn't fix the issue since Configuration objects
are not printed inte Arkane input files using __repr__.

We should generally have better unit tests that __repr__ reproduces things.

Author: rwest

rmgpy/pdep/configuration.pyx

@@ -73,6 +73,7 @@ cdef class Configuration(object):
         if self.sum_states is not None: string += 'sum_states={0}, '.format(self.sum_states)
         string += 'active_k_rotor={0}, '.format(self.active_k_rotor)
         string += 'active_j_rotor={0}, '.format(self.active_j_rotor)
+        if self.energy_correction != 0.0: string += 'energy_correction={0}, '.format(self.energy_correction)
         string += ')'
         return string