Added Batteries

[DanteNiewenhuis]

Summary

This PR adds batteries to OpenDC. Batteries are an alternate power source that can be charged and discharged depending on a BatteryPolicy.

The main use case for batteries is to reduce the carbon emissions of a data center.
The battery is charged when green energy is available.
Later, the energy stored in the battery is used when no green energy is available.

Batteries fit into the FlowGraph in the following way:

Adding a battery adds four new nodes:

• A Battery of type SimBattery which can store energy
• An extra distributor that can distribute energy between the battery and the hosts
• An aggregator that takes energy from either the powerSource, or the battery
• A Battery Policy that decides when the battery is charging, discharging, or idle

Currently, a single battery policy is implemented.
This policy works with a single carbon threshold.
If the carbon intensity is lower than the threshold, the battery is being charged.
Otherwise, the battery is being discharged.

The topology json schema is extended with an optional "battery" field.

Simply specify none (N/A) if not applicable.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 0.00%. Comparing base (f471d06) to head (e9de393).
Report is 1 commits behind head on master.

Additional details and impacted files

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