REDD convert now removes any DualSupply appliances with only a single
supply.  I'm still not sure with some of the DualSupply REDD
appliances.  I am coming round to the idea of just scrapping the whole
DualSupply idea.  I still think it's a valid idea but it does produce
a lot of implementation headaches, and it's tricky to figure out
what's happening with dual supply appliances.

* Also fixed bug with plot_series