replace hoodie.account.ownerHash with hoodie.id()

see https://github.com/hoodiehq/hoodie.js/blob/master/src/hoodie/account.js#L1112

And I like the API, every user, no matter if signed up or not, has a **Hoodie ID**, that persists, and that can be used by apps or plugin devs for whatever.

- [ ] hoodiehq/hoodie-plugins-manager#12
- [ ] hoodiehq/hoodie-plugin-users#12