Provide a command line tool to run jobs #103

Swift/T, and other non-python or shell based projects, in order to use PSI/J, would need a command-line interface to running jobs. This issue is here to discuss the requirements, come up with a design, and track the implementation.

• an initial task would be to attempt to gather requirements from teams that are potential users of such a feature (@j-woz mentioned one such team).
• an initial rough design is based on the idea that one needs to communicate a JobSpec (and properties) and executor + config from one process to the other; this would be done through some serialization mechanism, which could take the form of:
  • command line arguments (e.g., --spec.attributes.duration=...)
  • json
• we talked about a sync vs async interface and concluded that the biggest benefit/cost ratio would be achieved with a sync implementation, since more complex projects would use higher level tooling; for reference:
  • sync here means run-job ... which exits when the job completes
  • async implies a set of tools, such as submit-job, cancel-job, job-status; there is considerably more complexity in implementing these, at least in layer 0 (basically these would roughly be a local version of layer 1)