Introduce a WaypointList class to define the interface to our lists of waypoints...

 Introduce a WaypointList class to define the interface to our lists of waypoints. (#326)

* Introduce a WaypointList class to define the interface to our lists of waypoints.

WaypointList is backed QList, eliminating the use of legacy queues for waypoint lists.

* try to appease xcode wrt std::abs.

* clean up inheritence in WaypointList, RouteList.

also quiet clazy with igc and gpsbabel_optional::optional.
also improve includes in defs.h.

* get rid of unnecessary reinterpret_cast.

and correct pointer constness lost by auto.