* Add kWh as cost option for GAS
* Add kWh as cost option for GAS (pylint)
* Add kWh as cost option for GAS (make CONST)
* Change GAS_UNITS to VALID_ENERGY_UNITS
* Add test for Gas cost in kWh (2)
* Back off ENERGY_WATT_HOUR - unlikely for gas
* Add MEGA_WATT_HOUR support (2)
* Normalise pricing for MEGA_WATT_HOUR
* Normalise pricing for MEGA_WATT_HOUR