Minor clean-up

[joseph-robertson]

Pull Request Description

Items:

• Remove empty resstock-measures README; remove LICENSE; planned to connect measures folder to separate repo at one point in time, but that never happened.
• Remove extra stuff around heat_pump_backup_use_existing_system in ResStockArguments and ApplyUpgrade; turns out this is not needed because we are reading heat_pump_backup_use_existing_system from the measures hash and not from new_runner.

Checklist

Not all may apply:

• Tests (and test files) have been updated
• Documentation has been updated
  • If related to resstock-estimation, checklist includes data dictionary, source report, options saturation, options_lookup.
• Changelog has been updated
• openstudio tasks.rb update_measures has been run
• No unexpected regression test changes on CI (checked comparison artifacts)