Feature/provisioner workerdata

this is the simplest, most direct way to point the workers at the synced data directory.  I'd like to revisit a lot of the worker, but this will work in the short-term.
- [x] --work-dir passed to worker as an argument
- [x] plugins are initialized with an ``@env`` instance var, which can be used to retrieve all configuration options in the worker.  this is one place we could probably figure out a better interface for the plugin author.  the current behavior of overriding initialize is kinda ugly.