mongo: use SKIP_DEP_TESTS again. regressed in recent refactor.

Noticed because 'make presubmit' was breaking when offline.

Change-Id: I1afd12eb2ae8f504018b8a30a91d2d2e87d35999
server: unexport some image stuff, add docs, TODOs, clean up

Change-Id: I4914de33406da08a4bbf806d9d0386a285e4a8d7
Limit number of image resizes happening at once.

Attempt to ease memory spikes.

Change-Id: I4df7177c063b284ac841335d8f18b1a6da5289d0
Unexport UIHandler's PublishRoots

Change-Id: I844d2f0cd7ef2b81caf3035ed8abaeef023b90ee
Thumbnail cleanups and let the meta map persist on disk with a sorted.KeyValue

Previously, every time you restarted the server, it forgot about all
thumbnails previously generated.  (in practice it didn't/doesn't
matter with a single user, though, since they're still cached in the
browser and we always reply to If-Modified-Since immediately without
checking the cache)  But it'll matter more with the Publish handler.

Also, rename some stuff, clean up some stuff, drop an unused interface.

And then necessarily change the serverconfig low-level generator to use
a kvfile for the thumbmeta map when using local disk for blobs.

--

Change-Id: I4dcfcb21429a440aa118794c03f7abf7bd69c33b
More thumbnail cleanup, in prep for putting singleflight in.

Change-Id: I11c60ee7d14f330c20ca916fbce963d3c59d561f
Use singleflight when generating thumbnails.

Change-Id: I3691f912748a85db09f96029584129e0897191ef
images: performance and memory improvements.

Makes the assumption that our old image logic was 'If the image is
huge (>2400px) shrink it to twice the target thumbnail size with
resample (which is quick) then box filter the image in half (which is
slow)'.  There was a bug there that was causing large intermediary
images to be allocated when the source image was just the right size
and in portrait orientation (mainly trigger by photos from my Nexus 4).

Generalizes resize code to always resample to 2 times the thumbnail
size and then smooth down.  Throws more pixels away faster.

Add downsizing routines that operate inplace.  This greatly reduces
our peak memory usage when generating thumbnails.

Add version optimized for our particular resize case (halving);
providing a speed boost over the generalized versions.

Add tests and benchmarks comparing new resize to old.

Test for pkg/misc/resize can be run with --output=output_dir/ to see
the images generated by the old and new resize routines along with
mask of their differences.

Addresses some of the concerns in https://camlistore.org/issue/237

Change-Id: I6464fa637da9db371f15761bb699c045604b6cb8
Merge "images: performance and memory improvements."
Merge branch 'master' of https://camlistore.googlesource.com/camlistore

Conflicts:
	pkg/server/image.go

Change-Id: Ieae89d752f4c6602e0ce31f90e719b07612acb43