Implement a simple forking option

[ehmatthes]

Implement a simple forking option when creating a new school, so new users can use one of the site's main strengths - not having to reinvent the wheel. Copy all elements, but no editor relationships.

• What are the critical tests to write?
• Where do the links to do this exist?
• What's the workflow for doing this?

[ehmatthes]

• [ ] Critical tests: (see #103)
  • [ ] Rejects a non-empty organization.
  • [ ] Check that only public organizations can be forked.
  • [x] Fork an organization, and make sure all elements in the new organization match the old organization.
  • [ ] Check there's nothing in new org that's not in old org.
  • [ ] Make sure original org is unchanged, in all aspects.
  • [ ] Add a new sa to old organization, make sure it's in old organization and not in new organization.
  • [ ] Add new sa to new organization, make sure it's in new organization and not in old organization.
  • [x] Make sure user forking is the only editor of the new organization.
• [x] Further tests:
  • [x] Make sure only public elements are in new org. (Actually, easy enough to do in checking that systems match.)

[ehmatthes]

• [x] UI/ links
  • [x] User creates a new organization.
  • [x] On the organization page, after stating no elements, link to fork.
  • [x] On forking page, can only fork public orgs now. (Later, could fork private orgs that you have edit access on.)
  • [x] utils.fork() only copies public elements.
  • [ ] Will need to report errors in forking process to user. later (#100)

[ehmatthes]

Rest of the tests moved to #103.