Show server errors in the piggy menu.

When there is a server error, the piggy becomes sad and periodically
shakes his head. When you expand the piggy menu you see one or more
entries explaining why he is sad.

Change-Id: If1e28dbf02c9befaa46b62838cb704220f719bc6
Adjust position of error icon.

Change-Id: I2b86d8b52a3c616ca3f2408973d85e70fb27a2d7
blobpacked: first cut at packing, creating zip files with contiguous chunks.

See package docs in blobpacked.go for background & rationale.

Will minimize disk seeks, regardless of the underlying storage
system. I always knew this day would come, but we've been putting it
off. It's finally time to separate out logical (tons of small chunks)
storage from physical (big contiguous layout for how they'll be
accessed).

First 80% is done. Last 80% remains: mostly lots of tests and more
paranoia, and fsck things, for when we inevitably lose indexes. (but
each zip file is self-describing, so the index is redundant).

Change-Id: I13f9aa79c4d9d87b5fdcece0d99d97eba031d608
Merge branch 'master' of https://camlistore.googlesource.com/camlistore