Adding worker_version to ExternalAbstractNgenRequest to be able to
specify a requested version of a job worker.

Updating Launcher determine_image_for_job to use supplied worker_version
value from originating request for ngen-type request objects, rather
than always defaulting to "latest."

Move scheduler package internal dependency on communication to 0.22.0.

Updating client package internal dependency on communication to 0.22.0.

Updating requestservice internal dependency on communication to 0.22.0.

Updating schedulerservice dependencies on communication to 0.22.0 and
scheduler to 0.14.0.

Instead of just external subclass.