Implement tweaked model which predicts single timeseries at once

[JackKelly]

• Need to figure out how to elegantly handle nighttime PV data
• add NWP into the target query
• implement RNN. That try without direct input of history, to start with
• enable RawPVDataSource to set the location of half the examples, and implement Only have one of each RawDataSource in RawDataset #78
• Reduce duplication between PVQueryGenerator and GSPQueryGenerator #144