Removes storing variants of the image.

The original image will be stored for all sizes of the image. There are also some libraries that were removed because they were unnecessary and some options that were added.
Merge branch 'ohmage-2.16' of github.com:cens/ohmageServer into ohmage-2.16-image_issue
Fixed the image issue by creating a background process.

There now exists a background process that will create the image variants. This will allow uploads to still be very fast. In the event that someone asks for a copy of the image that has not yet been processed, it will be processed at the time it is requested and served.

Closes #594
References #451