Expose button to force syncing to happen NOW

Background:
Our current cron job only runs once every 10 minutes.  This means that there's a chance that a computer will be online, but syncing may not occur.

Changes:
* Expose a simple API endpoint for launching the `syncmodels` job (as an asynchronous process).
* Expose a button in the "eash_admin" page (on the distributed server), only when the distributed server is online.

Notes:
* With this checkin, we can expose this same button in other places / ways, if we like.