Umbrella bug to cover a few bundle download changes:
1) Since the recent addition of the merged bundle, we no longer need to download bundles which only contain classes (as opposed to DLLs, etc.) unless they are specifically requested. This results in a roughly 4MB reduction to the total download.
2) Background downloads need to be more intelligently ordered. Right now they are downloaded in arbitrary order, but frequently-requested bundles should get priority.
3) Some bundles.xml tuning to help avoid big bundle downloads to obtain a single class.