SD-395 : adding desks for given users ...
fix(python): make superdesk importable in python2.7

while superdesk might not run there, some parts can be reused
fix(media): skip exif meta that can't be json encoded

SD-381
SD-395 : adding desks for given users ...
Integrate rendition importing into archive_ingest feature
Merge remote-tracking branch 'mugur/desks'
Merge remote-tracking branch 'adrian/master'