Give "bin/worker" flags to repeat and retry tasks
Although it's good not to do these things by default (particularly, retrying a successful task will double its effects), there are plenty of cases where you want to re-run something for testing/development/debugging and don't care that the effect will repeat (you're in a dev environment, the effect doesn't matter, etc).
Test Plan: Ran bin/worker execute/retry against archived/successful tasks. Got prompted to add more flags, then got re-execution.
Reviewed By: amckinley
Maniphest Tasks: T13253
Differential Revision: https://secure.phabricator.com/D20246