Update the chord parameter packing in  in main_wing_planform

update naming to Wing.chords.root and Wing.chords.tip
Apply PEP8 formatting for wing planform files - not sure if these really conform to coding style.
Renamed chord_mid to chord_mid_trap to reflect trapezoidal wing. 
these spaces are in suave style, they put the equal signs on the same character column, so it reads like a table