Docker (linux): "Assembly reference 'netstandard' not found

Running via docker on linux for the first time in a brand new Notebook, I see an error message "Assembly reference 'netstandard' not found" with a simple addition statement.

There's a bit of a mismatch between the editor services and execution engine on Linux causing this. I don't recall if it's now fixed in master but the Docker image could be updated as a first step see #249 needing a volunteer.