Admins to enter core trac ticket number if editing parsed content

[siobhan]

#411 allows admins to edited the parsed content.

However, admins should not be able to save the content without adding the associated ticket number on core trac. This will ensure that all changes are passed upstream. Workflow should be:

1. Admin opens core trac ticket for docs change
2. Goes to code reference and makes change
3. Enters the trac ticket into a field - if the trac ticket # is entered they can publish the post, if not then it won't publish.

[DrewAPicture]

I've been working a proof of concept for this, which I think is inexplicably tied to comment:2:ticket:411.

[coffee2code]

In 831:

Code Reference: add admin interface to restrict access to editing parsed content

• Requires a core trac ticket number to be added in order to edit the parsed short and long descriptions to ensure changes got reported to core
• Ensure only admins can edit parsed content

fixes #411, #481.
props DrewAPicture