p51d-jsbsim - cockpit improvements

p51d-jsbsim - cockpit improvements

1. Floor boards are now black in historic version.  Still bar wood in YASim version.
2. Floor boards now expose subfloor around stick and under console.
3. Stick has added boot.
4. Increase smoothness of rear left cockpit wall.
5. Add hole in rear left cockpit wall for flap control.
6. New textures for cockpit light control plat, flap control, subfloor and stick boot.  Textures are still flat/basic.