Short term:

- test max_concurrent restriction to limit number of stages running concurrently

- add pod docs to ModuleLoad

- add pod docs about resources_required

- module load
    - option to get modules from $ENV{LOADEDMODULES}
      - instead of user-provided list

Medium term:

- write a porting guid to driver writers

- write a 'driver' to display ordering from stage pre_req/dep info
