Add an option to engage brakes when vessel is focused and BV is engaged

[Lisias]

Focusing a craft controlled by BV can be frustrating if the craft is on a slope, because you can't switch off the damned thing until it stops moving. What can be slightly annoying if you was climbing a mountain...

Engaging BV while the craft is focused should automatically engage the brakes. Focusing a BV controlled craft should automatically engage the breaks.

Obviously, this feature should be deactiveable at user's choice.