allow bundle selection for entity autocreate

PR created. I also fixed the outdated reference to "terms" (rather than entities) in the autocreate option description while I was at it.

Thanks for the MR, I plan to look at it later. For now, just noting that it looks like an issue for this already existed: 🐛 Feeds term reference select vocabulary Closed: duplicate .
Referencing, so both can be closed once one of them reaches the fixed state.

Oh, and tests for this feature are welcome of course.

I've added test coverage and fixed a coding standards issue. For the rest, it looks good to me.

I merged the code! Thanks for your contribution.

Automatically closed - issue fixed for 2 weeks with no activity.