Aggregate DHW vs. CH data for systems (where available)

[MrTimbones]

My Heatpump app can take a feed that signals when DHW is running vs. CH, and provides kWh and COP numbers for each.

Several people have asked for that same information to be aggregated by HeatpumpMonitor so that systems can be compared on equivalent merits.

Quotes from this discussion

The biggest variable when attempting to compare my own system performance (in isolation or against other systems) from one day to the next is dhw vs heating energy.
Being able to specifically focus the top level chart on either just dhw or just space heating would make comparisons much simpler and more relevant.

DHW usage quantity varies widely according to personal circumstances and has such a huge effect on SCOP. trying to compare against another system to figure out if they’ve done a better job than you (so you can ask them how!) would be so much easier if DHW can be filtered out.

This will require careful consideration, cos:

• not all systems have configured DHW feeds
• increases the data that will need to be collected from every system and stored

[MrTimbones]

From issue #12:

• How many kWh of heat does the heat pump send to DHW?
• What proportion of the time does the heat pump spend on DHW versus CH?
• What quantity of DHW is being consumed by the household (litres per day if that is metered)?