camlistored: signal typo s/SIGTERM/SIGINT/

Change-Id: I1111cd4911b08c3d6e8459916358432cb52ed6a1
index: bunch of TODOs and planning for edge tracking

Also, change to storing a pointer to claims so those pointers can be re-used elsewhere.

Change-Id: Ib0979d622ba48f1e2389575d07d7a0930264ebea
Merge "camlistored: signal typo s/SIGTERM/SIGINT/"
add compression to diskpacked

Initial commit for implementing compression in diskpacked
- with fixed ratio of 0.75 (no compressed storage if the saving is
less than 25%), zlib compression method, default level.

As blob.fetcherToSeekerWrapper.Fetch erroneously asserts that FetchStreaming
returns a ReadSeekCloser everytime, it had to be changed.
This is addressed with a readerutil.MakeReadSeekCloser
(pkg/readerutil/memfile.go) which slurps the reader into memory, or spoils
it to temp file if too big.

This utility now is also used in pkg/blobserver/diskpacked.ReceiveBlobs.

Change-Id: I5ee59c2ac325768f0e29a4dfee9a437f6f1384bd