Not just in blob.SizedRef, but in blobserver.Fetch and
blobserver.FetchStreaming, too.
Blobs have a max size of 10-32 MB anyway, and the index.Corpus is now using
uint32 to save memory.
Change-Id: I1172445c2f9463fdaee55bfe0f1218d44be4aa53
Bytes read/writen per pack file, as well as per configured diskpacked
configuration are now available as expvars.
Also add reader stat helpers to pkg/types and updated the original
user in server/image.go
Change-Id: Ifc9d76c57aab329d4b947e9a4ef9eac008bc608d
Tamás Gulácsi