Fiat: add PIN support and start/stop

[FraBoCH]

Is your feature request related to a problem? Please describe. When charging a Fiat on TWC3 (or other non-controllable charger), evcc cannot start or stop charge.

Describe the solution you'd like The API provide a start charge action => we could use that. https://github.com/TA2k/ioBroker.fiat managed to implement changing the charging schedules. My proposition is that evcc manage 1 of the 3 schedules available to simulate a stop request. In practice:

• when starting charge: update schedule with start time = current time (to be consistent)
• when in mode pv and not enough solar: update schedule with end time = current time + disable duration (few minutes generally)
• when manually switching to off: update schedule with end time = current time

Describe alternatives you've considered Manually editing the start schedule every day according to solar forecast + automation in HA to send notifications to me & my wife when we need to force start or stop charge manually by physically pressing the button on the car. Yes, I’m doing that, my wife not so much ;-)