Edited code reference content should be flagged

[siobhan]

Site admins will be able to edit the code reference content (#411). However, we need to keep track of what has been edited so that patches can be created for core to a) ensure parity, b) ensure that important changes are preserved after the parser is run (thus overwriting everything).

We need some sort of internal flagging system so that we can keep track of what has changed. This way the docs team can review all changes prior to an update and make sure that patches are submitted as necessary.

[siobhan]

Closing. See #481