Person and Organization page enhancements

This is a rather big pull request that tries to bring a bit of sanity to the person and organization editing interfaces. I expect there will still be more design-y bits to come after this, but hopefully this makes it a little bit easier to work with and make changes to those pages!

Some highlights:

- Added suggestions form for anonymous users to suggest edits
- Changed a lot of javascript powered links to be real links (which also fixes an intermittent bug with the "new organization" button).
- Made some progress towards separating the templates for viewing/editing organizations/people
- Made the edit forms use actual `<form>` tags and do an actual POST request to the server
- Moved org/person saving logic into org/person apps rather than going directly to the API, this allows us to hook into the request and do things like saving memberships.
- Added integration to popit-api's models, which are now exposed through the `req.db.model` method, this will hopefully help us work towards https://github.com/mysociety/popit/issues/264
- Trimmed down the amount of client-side javascript that's needed (a bit)

Part of https://github.com/mysociety/popit/issues/468, https://github.com/mysociety/popit/issues/488 and https://github.com/mysociety/popit/issues/504

Fixes https://github.com/mysociety/popit/issues/491
Fixes https://github.com/mysociety/popit/issues/492
Fixes https://github.com/mysociety/popit/issues/494