Rename ViewService to ProjectService.
Work in progress for thumbnail/image/blobstore handling.
Make secure/signed image urls.  Project will now only refer to image
urls from our app/domain and not to any third party sites.
Ensure that we don't inadvertently serve non-image content as images.
This currently restricts us to PNG and JPEG via explicit magic number
checks.
Add caching for image handler.  These will be static so we want to get
the maximum amount of caching.