Makeflow / Work Queue Environment Support

Makeflow now cleanly generates a list of environment variables for each job, which is passed through the batch job interface to each driver.  Condor/Cluster drivers export variables before submission, while Chirp/WQ pass the variables explicitly down the pipe to the job and then setenv at the execution site.  

Along the way, I cleaned up the batch job interface by consolidate submit() and submit_simple() (the former was entirely unused), simplifying support for the combined cluster systems, and dropping support for hadoop, which was rickety and unused.

Cleaned up docs to correspond.