pkg/server: set thumbnail RAM limit per-handler.

Move from one pool for all thumbnail resizing to per-ImageHandler
instace.

Uses the value of "maxResizeBytes" if specified in the "handlerArgs"
section of a "publish" or "ui" handler's low-level config.

If we end up wanting to share pools, i.e. if all published
handlers should share a pool, we'll need to do a bit more work.

Implements suggestion from https://camlistore.org/r/1803 review.
Further improves on https://camlistore.org/issue/316.

Change-Id: Ia93fad119b546064173ac3e2c7f0ab8509744628
pkg/client: multi servers config

http://camlistore.org/issue/309

Change-Id: I22bbbf6a808a772272f153b2535d693bd986d13a
Merge "pkg/client: multi servers config"
Merge "pkg/server: set thumbnail RAM limit per-handler."
Fix Fetch -> FetchStreaming conversion

As blob.fetcherToSeekerWrapper.Fetch erroneously asserts that FetchStreaming
returns a ReadSeekCloser everytime, it had to be changed.

Move MaxBlobSize from blobserver to constants (new package).

Change-Id: I4b4f22c302cbec84d77d21454e0c9e8aebdf73e5
Merge "Fix Fetch -> FetchStreaming conversion"
clientconfig: forgot to git add it with bf8c463d0a569787e3600f57bf2109cf08b6bf29

Change-Id: I098fd8c3297c48f0800f5753d220fe706601a16b
year++

Change-Id: Ib5e17c39d3178357e1c18c4407ad45e91170ef16
Move defaultMaxResizeBytes to pkg/constants

Change-Id: Ibb5f82b6f33a4417649f1538a996f1fe7eac885e