Improve (client side) bind performance

Certlib update (2+ server calls, and some disk io) will happen in a thread, and do not block the gui anymore.  While the actual bind occurs, we will show a progress bar, much like refresh pools.

We should keep in mind that UEPConnection.bindByEntitlementPool returns the list of entitlements bound (always len 1 in this case).  That cannot replace certlib.update because of modifier products, but if we serialize it from the json response, certlib.update will have one less serial to pull down.  That could be a bit change though, because we have to trigger the same callbacks (branding hook, repo hook etc).