[Reviewer Andy] Dynamic Sproutlet loading

Andy

Can you review the changes for dynamic sproutlet loading.  I'll email updated spec separately.

Mike
There were fears that, if they weren't co-located then the database becomes the communication channel and Jeff Bezos would bring the thunder.

Possibly this could be fixed by having `memento-as`, `memento-http` and `memento` so you can one-shot a co-located install or install separately if you have more elaborate needs.