21 context menu backend

[thomasgwatson]

This is just the backend for #21

I'm wary of continuing to write out a massive feature branch, with changes to backend, mobile and web, without some level of periodic merging of code into dev. Just going to set us up for massive merge conflicts, particularly once we start re-structuring existing parts of the platform (chat's backend comes to mind).

This change-set is safe to merge. There are still backend changes required, but I want to now focus on web UI changes

Backend changes I am still anticipating:

• adapting to the new chat data model
• Data migration from old context menu to new (There is a Group method that does this but no overall process to apply it across the platform)
• Functions to determine activity metrics for each widget/view (highlightNumber and secondaryNumber). What these numbers represent aren't specced out fully yet, and will likely require different rules for different types of views
• process to check if content/group creation requires changes to the groups context menu (most of this logical is covered by transitionToNewMenu function)