18.4: Added recent descriptions button when adding new waypoint. Backup waypoints before deleting waypoints and/or tracklogs as well as when exiting the app. Cancel GPS updates properly when closing app.

18.2: Added auto backup of waypoints and tracklogs when exit button pressed (Cycles three backup files. This is for emergency use if data lost). Show grid ref using last known position. Swapped altitude and acccuracy on main page for consistency with other versions of app.