Implement more advanced submitter/scheduler framework

[jhclark]

Currently, submitters only allow a "run" action, but they should also allow the following actions (mutually exclusive with "run"):

• submit
• get_q (static, shared among all tasks using this submitter)
• check_job (if job is not done, loop back to get_q)
• check_exit

This will allow us to resume or kill previously submitted jobs if ducttape dies or is killed. It will also allow the user to more closely monitor the progress of jobs getting submitted.

[jhclark]

These usage patterns should potentially be documented with cute OmniGraffle images.