Improving current code

NEED TO IMPROVE AN ALREADY WORKING CONSTRUCTOR. (I have included the images). Currently only GPX format is recognised on my code, but the intention is to extend this to include one or more NMEA sentence types in the future. The program needs to be prepared so that in the future NMEA sentence types can easily be implemented. Modifying the route constructor gpxp::Route::Route(std::string), but code review has indicated that better modularity would make integrating further formats more straightforward and the code more robust. The code needs to include comments that are clear and easy to understand that will allow and future programmers (if required) to continue working on the code. The main intention is to commentate on the revisions, which should refer to the changes and the reasoning behind them. Summary: Code improved by refactoring with better modularity and should be able to accommodate NMEA file types in the future; commenting is essential.