Handle dual fuel measures

[jtlangevin]

Consumers may switch to a heat pump but keep original fuel as backup; the effects of partial remaining fossil fuel use on energy/emissions/costs should be accounted for in the Scout measure preparation module, ecm_prep.

Proposed approach:

• Create measures with a “backup_fuel_fraction” parameter that points to supplemental data needed to determine the fraction of remaining original fuel use for the measure.
• Develop a CSV for each measure in (a) that specifies remaining backup fuel use fraction (as a % of original total fuel use) by fuel and each region and building type the measure applies to.
• Loop through all applicable baseline fuel segments for the measure and run the following adjustments to efficient case data (in partition_microsegment function) for each:
  • Increase in original fuel energy use = original fuel energy use * relevant fraction from (b)
  • Decrease in switched fuel energy use = switched fuel energy use * (1 - fraction from (b))
  • Adjusted efficient energy data = original efficient energy + c.i - c.ii
• Repeat step (c) with additional multiplication by emissions factors and energy costs to get adjusted measure efficient emissions and energy cost results

[jtlangevin]

Initially added in commit 68b7de6, with associated measure updates in commit 0723550; needs unit testing.