Handle default language and its translations at once

I encountered the same issue, that I wanted entities to be imported with all their translations. I created an issue-fork here with an implementation of a new import processor that imports entities with all their translations. Feel free to test it.

I have updated the issue fork/MR to target 4.0.x and expanded the pull form to include a language selector. The selector allow to select the language in which the entities should be fetched from the remote.