Admin APIs, library upgrades, and misc cleanup

This tackles a few things:

- Abstracting the admin APIs and allowing admins to call them remotely with a private admin token.
- Upgrade library dependencies
- Cleanup how most javascript assets are vendored to use rails-assets.org, instead of git submodules.
- Ember-ify the admin user management.
- Use datatables on the api backends list for better standardization.
- Allow sorting of the api backends to fix https://github.com/NREL/api-umbrella/issues/21
- Better progress display on the datatables, so it's more obvious when the datatable is being loaded remotely on a long table.