Update generated formulas to use new naming scheme

[sahas-subramanian-frequenz]

Updated proposal:

• Terminology follows {component}_{quantity} and {component}_{consumption,production}_{quantity}.
• Components are: grid, battery, consumer and individual active components pv, chp, wind.

Using the example of power:

• grid_power: Can be positive (consumption from the grid) or negative (production into the grid).
• {battery,ev}_power: Can be positive (charge battery) or negative (discharge battery). Equivalently for EV charging station.
• {pv,chp,wind}_power: Active components, the power from local (renewable) generation. Negative if electric power is generated, otherwise zero or positive in case of self-consumption of the generator. (alternative terms: generation, supply, source, active)
• consumer_power: This aggregates the remaining parts not covered by the above metrics. Under normal circumstances this is expected to correspond to the gross consumption of the site excluding active parts and battery. The implementation should still support negative values to also handle exotic site topologies (e.g. unidentified generators) and sudden short-term effects. (alternative terms: load, demand, sink, passive)

In addition to that, for each of the above there will two additional metrics:

• {component}_consumption_power: Positive power value if {component}_power is positive, otherwise zero.
• {component}_production_power: Positive power value if {component}_power is negative, otherwise zero.

Remarks:

• Gross consumption: Consumption before accounting for any local generation from solar, wind or CHP.
• Net consumption/load: This term traditionally refers to the difference between the gross electricity consumption and the local generation (like PV production). This is the electricity consumption that needs to be met by the battery or from the main grid. This means consumer_power + {pv,chp,wind}_power (note that latter is negative when electricity is produced). Since this term caused confusion in the past, it's not included in this proposal.
• Residual consumption/load: In microgrid context sometimes used as the remaining difference between the net consumption and the battery power, i.e. what we define as grid power.
• Consumer: Term deliberately chosen to indicate that this component is expected to predominantly consume electric power. Under normal circumstances there should be no active sources in this metric and the metrics consumer_{consumption,production}_power would not be used.

Originally posted by @cwasicki in #318 (comment)