Adapt stationfinder search conditions

[m-kro]

Currently the stationfinder device does not reroute to a charging station if the battery charge still allows to reach the destination. If the battery charge sinks below a threshold the rescue action is triggered.

Given the uncertainty of the predicted energy consumption, this may lead to vehicles breaking down in corner cases with extreme values (low battery capacity, low charge, short route). Instead the planned battery charge at arrival should not go below the rescue threshold.