Feature/water heater update

[afontani]

Pull Request Description

Companion PR: resstock-estimation #87

This pull request updates the water heater housing characteristics.

Current Structure

• A single housing characteristic Water Heater.tsv.
• We currently do not model premium water heater options.
• We currently do not model heat pump water heaters.

New Structure

• New housing characteristics Water Heater In Unit.tsv that is used to potentially separate out energy for central water heaters.
• The Water Heater.tsv is split into 2 housing characteristics.
  • Water Heater Fuel.tsv: The fuel of the water heater.
  • Water Heater Efficiency.tsv: The efficiency and type (tank/tankless) of the water heater

New options being modeled

• Water heater blanket is used as a proxy for premium storage tank water heaters.
• Heat pump water heaters are now modeled and are 0.5% of the electric water heaters in the stock except in the Pacific Northwest (CR06) where they are 3% of the electric water heaters.

Checklist

Not all may apply:

• Unit tests have been added or updated
• All rake tasks have been run, and pass
• Documentation has been modified appropriately
• Any new options are added to project_testing
• project_testing runs without any failures
• No unexpected regression test changes
• All tests are passing (green) on circleci
• The changelog has been updated appropriately
• This branch is up-to-date with master

For more information on how to perform these checklist items, see the documentation's Advanced Tutorial.