Unique ID checks (show all error occurences)

[odscjames]

I've realised while putting these into the Cove UI that

• if a ID is used 3 times we want one error for that ID (currently you will get 2 errors)
• You want to see the path for each time the user ID is used (currently you won't see the first path, only subsequent ones)

[duncandewhurst]

I think it might be better to show 3 errors, that way there is only one ID and path per error, which is consistent with all the other error types.

[odscjames]

Moved heading error to https://github.com/Open-Telecoms-Data/cove-ofds/issues/64 - deleted from comment above

[duncandewhurst]

Edit: Ignore me, it was a different check.

[odscjames]

I think it might be better to show 3 errors, that way there is only one ID and path per error, which is consistent with all the other error types.

That will just start happening next time we release a version of this library and update cove to use it (already tested).