Code reference content should only be editable by admins

[siobhan]

In the code reference, the inline docs are parsed into the content field in WordPress. The should only be editable by site admins.

Therefore, the content for all code reference post types should be blocked for editing to anyone who's not an admin.

[DrewAPicture]

I worked on a solution for this over the weekend and should have something to share soon.

It will have to be paired with a pull request on the parser since I'm planning to argue that we move the parsed content out of the post content into meta (so we can use the editor primarily for explanations).

[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