GPFA now can include energies

[stevetorr]

Adapted from the Pymatgen PR template.

Summary

TrajectoryTrainer now has an include_energies argument which adds in structures labeled by energy during the active learning and passive learning training loops whenever frames are added.

• Code is in the standard Python style.
  Run Black on your local machine.
• Docstrings have been added in the Sphinx docstring format.
• Type annotations are highly encouraged.
• Tests have been added for any new functionality or bug fixes.
• All existing tests pass.

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[stevetorr]

Closes #281