Submit: show stdout/stderr of spawned process

[antiguru]

Currently, a submit commands runs the submitted job on some executor. Log files containing the stdout/stderr are created on the executor. That makes debugging a bit harder than necessary. Hence, I suggest a different mode for running Strymon submit in foreground. In this mode, the job would not be detached but the submit command would continue to show the stdout/stderr streams.

This can be implemented in two stages.

1. Provide support for running local jobs in foreground as the log files are locally available
2. Add support for remotely executing jobs