Clients process descriptor fetches as they arrive?

While we're fetching descriptors in a directory request, wouldn't it be nice if we could parse and make use of the ones that are sitting on the buffer?

This would let us bootstrap quicker, and be especially relevant once we use the fallback consensus and start using slow dir caches to bootstrap.

It will also avoid the 250K blobs sitting in ram.

This might be destabilizing enough that it should wait til 0.2.1.x. Not sure.

[Automatically added by flyspray2trac: Operating System: All]