Tidy up accounts. Serialise/deserialise not ok

- [ ] Ready for merge

Still needs some work to get the syncing working. Got a feeling I might have to delete the code, re-plan and do it again (because there's a number of different ways it can happen).

- [ ] settings saving and restoring
- [ ] settings applied to out of focus tabs?
- [x] requires memcache sessions to be in place so we can invalidate them via the settings save