[WIP] As a new org user, I want to type organization name instead of First/Last name on register & edit account forms

- [ ] Add `only_organizations` to `community`
- [ ] Add `is_organization` to `people`
- [ ] When registering, show Organization name instead of First/Last if only organizations. Store it as `given_name`
- [ ] At edit user form, show org name, instead of first/last if `is_organization`