jsonalchemy: fix `six.iteritems` typo

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
documents: fix for model creation

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
jsonalchemy: import and PEP8 fixes

Co-authored-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
Signed-off-by: Adrian-Tudor Panescu <adrian.tudor.panescu@cern.ch>
jsonalchemy: UUID validation fix

Signed-off-by: Adrian-Tudor Panescu <adrian.tudor.panescu@cern.ch>