Added mean motion to `State` objects
Added mean motion to `State` objects

newlawrence/poliastro,poliastro/poliastro,newlawrence/poliastro,newlawrence/poliastro,anhiga/poliastro,anhiga/poliastro,Juanlu001/poliastro,Juanlu001/poliastro,anhiga/poliastro,Juanlu001/poliastro