[NEMO-devel] new constraint

[Ben Elliston]

Hi,

I've added a new optional constraint to the model (controlled with a new
command line option --min-regional-generation) at the request of a user
at UNSW.  My changelog message explains it well enough:

Author: Ben Elliston <b.elliston at unsw.edu.au>
Date:   Mon Sep 7 21:09:21 2015 +1000

    * evolve.py: Add --min-regional-generation option which sets an
      optional constraint for the minimum share of energy that must be
      generated inside each region. For example,
--min-regional-generation=1.0
      will ensure that no energy exchanges occur between any region, and
      0.0 mimics a copper plate.

Cheers,
Ben