Update to templates to use foreground mode

When using Alex's experimental --foreground branch (for testing), you can pass
--has-foreground to 'gear daemon' to have it generate templates for foreground.
This removes the --fork option in the API - a server is either using straight
up docker images, or foreground mode.  Foreground mode will be the default
execution mode when upstream lands their run-in-context changes.

Also, volumes are now properly linked from containers via --volumes-from