Release 8.x-1.0-beta1

We've done a lot of work since alpha4 to stabilize IEF and clean up certain parts.
The complex widget still needs a big refactoring, and there are other small ugly details, but we can start planning an initial beta.

Must:
#2494959: Add translation integration

Nice to have:
#2367235: Support entity revision references
#2653574: Unable to keep nested IEF data separate with multivalue fields.
#2569193: The simple widget doesn't support bundle-less entities

Released in alpha5:
#2649710: Required nested IEF forms don't work
#2674102: extractFormValues() fails to delete entities, save nested ones
#2673952: Add tests for reference form validation
#2673920: Rename #entity to #default_value in the form element
#2673966: Render the bundle without a link (in the table)

Released in alpha6:
#2664626: Add another item does NOT work the first time it is clicked on simple widget
#2672022: IEF field widget do not check for entity create and edit access
#2690093: The simple widget can't be embedded inside a complex one