Fixes #260. Fixes #261. First crack at system config page
Fixes #257. Functional settings page in web client
Closed registration behavior.

Also allow admin flag to be set at user creation time by admin users.
Add a test to make sure admin flag can't be set for normal registration
OAuth plugin should respect closed registration setting
Add some test coverage for the server config page
Use correct test for SMTP server setting value in web client test
Merge pull request #286 from girder/closed-registration

Closed registration