This change fixes up the rest of the spinners in the Review Board codebase to

use the FontAwesome "pulse" spinner. The ones in the New Review Request and

Update Diff UIs were replaced, and there were some outdated styles for loading

rich text that had spinners which were no longer used.
There are still a couple spinners that still use the old "spinner.gif" in the

Djblets extension and config forms UI. Those will get fixed up in a later

change.

Looked at the New Review Request and Update Diff UIs and verified that all the

spinners looked amazing.