Add V speeds

It would be great if critical V speeds (ex: V Ref, Landing reference speed & V S, Stall speed) were added to the sim. These would be data points that can be accessed from the in flight menus and displayed in the flight UI.

These speeds would be constantly computed throughout the flight as variables such as aircraft weight, OAT, etc change.

Having V speeds would really help us fine tune how we fly our aircraft in different flight regimes such as landing and maneuvering.

Here we are :)