Support for editing previous responses

[aidanbh]

What parts of the StrangeScout system does this involve?
JScout and GoScout

Is your feature request related to a problem? Please describe.
Definitely a major limitation.

Describe the solution you'd like
Instead of rejecting all duplicate primary keys, actually check if data is identical (compare all fields except timestamp), show diff to latest submitter (the one attempting to overwrite/change) and allow the user to return to editing, abandon, or overwrite. Make sure timestamps are visible in diff. Fancier features would include note merging, but that might best wait until user management is implemented.

Describe alternatives you've considered
This stops short of a full database UI, which requires a lot more planning and is of questionable use. However, the ability of end-users to edit incorrect or incomplete entries without a desktop, installed software, or special knowledge, is critical to a polished product.

Additional context
We should probably attempt to complete #20 ORM implementation in parallel/before this or we will just be adding more hardcoded SQL for that commit to cleanup.

Paired with CSV export (#24), this makes the system fully-functional without any SQL access or administration beyond the initial Compose deployment (as we experienced at IRI).