Fetch actual user on settings/users/user

Closes #3279

- Switch from this.session.get('user') to this.store.find('user') and
some further limiting until a custom user adapter is created
- Switch the deactivate logic to rollback the used model
- Pass the user as the model in the link-to in user list template
Merge pull request #3302 from jgable/fixUserMe

Fetch actual user in settings/users/user