Merge pull request #3798 from RosettaCommons/jadolfbr/sm_in_xmlobjects
This PR adds functions to access individual `SimpleMetrics` from the `XmlObject` class - which is useful for PyRosetta. The SM can call the apply function of the base SM, which will add the data to the pose. With #3797 it should now be easy to access the calculated SM data as a dict.
It should be noted that some functions, like `cached_calculate` and `calculate`, are not in the base class, and so, cannot be accessed in this way in PyRosetta without knowing which type of SM you are obtaining ahead of time. In C++, you can cast it.
Unit tests are updated to fully test these additions.