Refactor some of the SectionHelper code and add basic documentation
Refactor some of the SectionHelper code and add basic documentation

This code probably needs a deeper refactor as we develop our tag model, but in the meantime I'm trying to make it a little
clearer.

alphagov/panopticon,theodi/panopticon,theodi/panopticon,alphagov/panopticon,alphagov/panopticon,theodi/panopticon,alphagov/panopticon,theodi/panopticon