drush command default-content-export-module-with-references

I've created a new drush command that works with 2.0.x

I've tested the latest merge request from justafish and it works great.

Hiding the files, which were for the 8.x-1.x branch.

The only issue I have is that I'd like to be able to define entity types not to export, e.g. the "user" entity. For example, if I export a block that has a media item, which has a file record and then a file, which all point to a user object, the command exports the block, media, file items and the file itself, but not the user. That said, the improvement could be done as a follow-up.