Add iteration methods to nvpair.
Added nvpair_export.
Pass environment using an nvpair instead.  (much simpler)
Simplified Condor and SGE implementation to handle quoting correctly.
Reduce repeated code for environments.
Backslashes to ensure env is evaluated by task.
Cleaned up and documented cluster support, so that we use a consistent
mechanism across batch types.
Fixed up test.
Moved -V option back into specific batch job options, so that it
can be over-ridden.
Fixed typo in help.
Removed support for Hadoop, it was an experiment and not recommended for use.
Updated makeflow docs for latest features.