Add drain water heat exchanger methods to WaterUseConnections

[mdahlhausen]

This is a feature request to add these methods to the WaterUseConnections object:

• setDrainWaterHeatExchangerType
• setDrainWaterHeatExchangerDestination
• setDrainWaterHeatExchangerUFactorTimesArea

[tijcolem]

@joseph-robertson Scope the effort to support this?