CRUNCH-282: Add a parameter to control the maximum number of reducers for a job
CRUNCH-281: A proper fix for the issue originally handled by CRUNCH-237.
CRUNCH-283: Additional diagnostics for the planner dotfile.

1. Add the target dependencies that are implied by ParallelDoOptions
to the directed graphs (target -> PCollectionImpl)  as dotted lines
2. Add a label to each of the clustered subgraphs that includes the
Crunch JobID, to make it easier to map from running jobs to the
dotfile for diagnosis.

Signed-off-by: Josh Wills <jwills@apache.org>