Update the chord parameter packing in  in main_wing_planform; added generic fuselage; added new wing geometry calculation classes to compute exposed and flapped wings

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. 
rename this file and class to Cranked_Planform