add diskpacked storage system

Change-Id: Ieb16459c06d596ad49bbe78b6e058955fcd6f649
devcam: fix build

Change-Id: If5f8d6e0e4e315cd8ca01aa7bf9b0f59407c52fe
Merge "add diskpacked storage system"
Basic code to index id3 (and other audio) tags.

Does a few things:

1) Adds gotaglib to third_party. If you'd like to review that, feel
free, though there's a bit of organization I'd like to do first.

2) Adds an "audioTag" key type.

3) Indexes wholerefs by various audio tags. Doesn't yet add a map from
wholeref to tags, but I can add that next.

Change-Id: I8e2a5bc27260086bad3351ac57973d1ac23cff44
Merge "Basic code to index id3 (and other audio) tags."
Add new blobstore backend using Weed-FS

The main package is at pkg/blobserver/weedfs - modeled after pkg/blobserver/s3.

It uses some helpers for communicating with the Weed-FS master, in package
third_party/github.com/tgulacsi/weedfs-client. As this is only one http.go file,
maybe this could be incorporated in the weedfs package, as well.

Change-Id: I7940d47faabe63efb75c9e22b2d7715347092890