Refactor decorators

This is an effort to remove non-presentational logic from our decorators, they were becoming grab-bags of random functionality.

Any feedback on how I've re-jigged how related content generation with ``RelatedContent`` and ``CategoryContentHierarchy`` would be appreciated.
My initial version of this didn't do any decorating but when I hooked it up to the controller the view was expecting ``path`` and ``title`` which the decorators provide.

Any ideas of how to approach this that isn't a convoluted mess?