Easy client-side speedups

In this commit
* Cacheable.refresh now uses $.throttle instead of $.debounce.  The difference is that $.throttle kicks off immediately (which is what we wanted) while $.debounce waits for the interval first.
* 2sec after the initialization tasks, we start rendering Mustaches in the background by iterating over GGRC.Templates and calling can.view on all the ones not seen in can.view.cachedRenderers. (these operations are friendly-ish since each one is queued with GGRC.queue_event)
* The fake AJAX calls we do on $.ajaxTransport("text"...), which return a result from GGRC.Templates, now only do a single wait for all async calls to the same URL.  This wait uses requestAnimationFrame instead of setTimeout; the callback gets called faster than the usual 4ms setTimeout default this way.

Ref p/69640134 b/14272061