Embeddable Scripts

## Overview In addition to running separate commands with arguments it would be advantageous to also be able to embed scripts into the layout. ## Detailed Description Allowing scripts to be embedded inside the layout files would keep things tightly coupled where it makes sense. It would also simplify writing commands inline vs. the current command and argument lists. Having the ability to define scripts that are not just bash, but nodejs or python etc, using #!/bin/env <interpreter>