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. 
if you're IDE is deleting these spaces automatically, you can turn it off.  everyone's editors treat this style differently and it polutes the diffs and pull requests