Reinstate fmu.ensemble.etc for API compatibility

[berland]

Resolves #192

[ertomatic]

Can one of the admins verify this patch?

[markusdregi]

@berland: Any reason you are not introducing all of the etc module?

Besides that, the deprecation and testing of it is good 👏

[berland]

It is unlikely that there are user-scripts with anything else than what was in the documention, that is why I chose to only ensure that did not crash. I choose to not replicate exact logging behavior, rather trigger people to maintain their code.

[markusdregi]

Aight, if that was the only documented method I'm willing to accept that that was the only public part of the API... But, deprecated methods typically still function as expected. Are you sure you do not want to either introduce the old implementation of the function, or raise an exception instead of the deprecation warning?

[berland]

Aight, fully reinstated original code from v1.4.0, but with depr waraning. I envisioned it would trip other code, but it did not.

[markusdregi]

Looks good to me 👍