Initial groups functionality

Kanban tickets:
Create groups: https://aptivate.kanbantool.com/boards/5986-econsensus#tasks-2139615
See list of my groups: https://aptivate.kanbantool.com/boards/5986-econsensus#tasks-2139623
See list of groups I could join: https://aptivate.kanbantool.com/boards/5986-econsensus#tasks-2139627

This needs a lot of work still! More or less everything I did whilst in Cambridge. I'll send round an email soon about what I've done and what needs to happen next with this. Hopefully I'll find time next week to polish what I've done so far off and write some more tests.