test fetcher: add more stats

Change-Id: Iad880544174c812a49640939b8fb2922da738b28
schema: some FileReader cleanups: use blob.Ref as map key, simplify zeroReader

Change-Id: I37ec27bfe9673e7d5566216269d94d109215ac99
schema: reduce FileReader blob reads 32-85x by caching the last blob read

Little reads into big blobs kept re-reading the same blob.

Change-Id: I098c9d9a9443dacc93f60f96fff1edd421ced198
schema: more minor FileReader cleanups

Change-Id: Ia37d82024faf16c262f339d8f7f807d23670edda
Start of the 'blobpacked' storage type.

Change-Id: Ib8061edaa37c43553ced7eba06dd4baf1a984040
start of 0.9 release notes

Change-Id: I2a0ae60f0be17de99ad30c661981bc1baf1a57c7