Add transfer windows

Add transfer windows to orbits to make travelling from planet to planet easier.
How this works:
Once you make an orbit outside of droo, select your planet destination. After selecting your destination, in your craft's orbit you should see a transfer window then you lock prograde then time warp until you hit the transfer window and then you start turning the engines until the craft's orbit had an encounter to your planet's destination.
PLEASE ADD IT WOULD BE VERY USEFUL!