add preconditioning

[j-brendel]

We should add preconditioning to our simulation. Preconditioning is mainly used to pre heat the (cold) vehicle before leaving the depot using power from the grid via the charging station. In this time, the charging power available for the vehicle is reduced by the preconditioning power. e.g. If a CS has 150 kW power, but for 20 minutes before departure the vehicle is preconditioned with 30 kW, the vehilce can be charged with a miximum of 120 kW and 30 kW are converted to heat (for our model this is equal to losses).

This involves further inputs per vehicletype and charging type in vehicle_types.json:

• Preconditioning_time (in mins: time before vehicle departure from deps, where pre conditioning is applied)
• Preconditioning_power (in kW: Constant power applied during pre conditioning)