Add Energy Stage

Formerly named "SoC Stage", the Energy stage outputs values relating to energy in the battery.

Currently, the following products are outputted:

• EnergyVOLExtrapolated
  • Battery energy estimated using VoltageofLeast & SANYO NCR18650GA datasheet 2A discharge curve. See https://github.com/UBC-Solar/data_analysis/blob/main/soc_analysis/datasheet_voltage_soc/charge_voltage_energy.ipynb for details.
• IntegratedPackPower
  • The integral of pack power in watt-hours. Starts at zero for each event.
• EnergyFromIntegratedPower
  • Estimated energy in the battery in watt-hours. The starting value is given by the startingvalue of EnergyVOLExtrapolated, then IntegratedPackPower is subtracted from this. This technique of determining battery energy is equivalent to 'coulomb counting'. Values may be smoother than EnergyVOLExtrapolated and more accurate in the short term, but can diverge from the truth over time as systematic error is integrated.This value is also problematic if telemetry is missing values, as this will appear as if no power was used during this time.