Add column to store passholder photo in DB.

Previously, I've stored files outside of the database, and a path inside
the database. But, that comes with several problems;

   - special backup procedures required
   - filesystems aren't transactional
   - paths must match on all servers, or you get to do special path
     handling to translate them.
   - external file handling is invariably OS-specific. It might be nice
     if this were to run on Windows.

The advantages seem to be primarily when the files are large; in this
case we're talking small JPEGs... maybe 100k max.