Resolve "Provide convenient interface to define cuts via python"

Release notes

• Cuts can now be defined via python snippets in addition to (or in stead of) using TQFolder syntax config files. For an example see https://gitlab.cern.ch/atlas-caf/CAFExample/blob/master/share/xAOD/config/cuts/xAOD-Example-cuts.py

Details

The new python-only PyCut class is essentially nothing but a thin wrapper around TQFolders to make the creation of new cuts a more convenient and pythonic use.

Closes #205 (closed)