Add get_first_or_create method for CIVs

[amickan]

There can be multiple CIVs with the same interface and value/image/file in the DB. Retrieve the first of those if that's the case rather than throwing an error.

Closes #3594

[jmsmkn]

There is also a similar error for /api/v1/algorithms/jobs/, does this solve that too?

[amickan]

There is also a similar error for /api/v1/algorithms/jobs/, does this solve that too?

Now it does! Hadn't seen that error on sentry yet, and foolishly only searched the codebase for instances of ComponentInterface.objects.get... Sorry!

In retrieve_existing_civs, I think we should return all existing civs, not just the first though.