Lifetime time series buy and sell rates

[cpaulgilman]

Time series buy and sell rate inputs for retail electricity rates are for one year, but in some situations, the rates change from year to year, so it would be useful to have an option to provide time series rates over the entire analysis period.

This is related to Brian's rate switching comment at #301.

[cpaulgilman]

Suggestion from a user:

I think that probably the best solution would be to implement a form like this one:

Where one can put electricity rates for each future year.