Battery information should be made available through the API #102
Description
The API should expose battery/power information.
This should ideally include raw numbers like "available charge" and "voltage", "current", "remaining power", "consumed power". If possible, good to have an estimated flight time at current consumption.
It is possible for a vehicle to have multiple batteries, and the API should be capable of exposing the information for at least 2.
This issues resulted from #101