Update content "revised" field after a successful metadata update

Also ignore attempt to change the "created" field when updating content.

Close #100
Merge pull request #101 from Connexions/revised-date

Update content "revised" field after a successful metadata update
Add function to partially sync roles in publishing and back.
Add function to partially sync license acceptors in publishing.
Allow for 404 from publishing.
Add role and license acceptance route.