Add Image Metadata to Image Database

Three new keys:
* artist - Returned parsed text for the artist
* credit - Returned parsed text for credit description
  (e.g. the original source)
* licenseshortname - Short name for the license (e.g. Public domain)

Change-Id: I0abe839a1355b9ac80a3a79899db7980c95f0c0d
Merge "Add Image Metadata to Image Database"