Additions to PyGMO examples

[irmakcavdar]

It is not really clear from the current PyGMO examples when an aerodynamic coefficient interface or a thrust interface is set if it is included in the fitness function or in the general propagation file or in both. It gets a bit complicated to identify this from the current examples. Perhaps, it could be nice to provide few additions to current examples that shows where these attributes of the vehicle is included.