Bump is:pano threshold to 2.0.

Previous value of 1.6 was too small because iPhone 5's aspect ratio
is 1.78, meaning all landscape iPhone 5 photos were included in
is:pano. Same with Moto-X and probably other newer phones.

I tried 1.8, but it still "felt" too small. I think the correct
value is atleast 2.0, but perhaps larger. I don't have enough test
data in that range right now to get a good feel for it.

Change-Id: I6a3e054290d6f434afac8142a9abc68e53008229
Merge "Bump is:pano threshold to 2.0."
blobserver/s3: add manual test

Change-Id: I5854aecdb3e4d9e03a7cf56dc7901dc859821a46
Merge branch 'master' of https://camlistore.googlesource.com/camlistore