camput: delete command, to send a delete claim

http://camlistore.org/issue/191

Change-Id: I053ab468420cc173e6122909bf3a0b16e4d43224
Merge "camput: delete command, to send a delete claim"
Intern blob.Refs in the in-memory Corpus.

For me, saves 419054 blob.Refs and 10 MB of memory.  Before/after:

Before:
Corpus stats: 159.057 MiB mem: 787886 blobs (88.853 GiB) (279308 schema (6073 permanode, 150557 file (111819 image), ...)

After:
Corpus stats: 149.884 MiB mem: 787886 blobs (88.853 GiB) (279308 schema (6073 permanode, 150557 file (111819 image), ...)

Change-Id: Idf71011c14d0d9b7457beab86dd084651fc3b122
Merge branch 'master' of https://camlistore.googlesource.com/camlistore