diskpacked: keep fd open to every pack file.

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
Virtual scroll!

Change-Id: I3c564758f110975ecc1a5e6cf9a7db1777ade54b
Merge "Virtual scroll!"
Turn React-based UI on by default.

Change-Id: I7370954eb1fda679be25e3ab652fb3776c55c938
Merge "diskpacked: keep fd open to every pack file."
Throttle updates to history so the URL bar doesn't flicker so much.

Change-Id: Ie2b1cc8a6abe2d41083dcd1116940508b22661f5
Merge "Throttle updates to history so the URL bar doesn't flicker so much."
test: fix enumerate bug in in-memory storage when double-uploaded

Change-Id: I7e6abb1c9dfc61f39fa9d315857bf7aeb13b6b59
namespace: finish tests

Change-Id: Ib34364473e407e78fd691256ad1afe8c810911a9