Substantially bugfixed and improved deactivation/activation and persistence of widgets. A lot of testing of Google Earth view, only minor improvements

Fixed initial startup bugs, cleaned up the activation-deactivation of update timers. Added initial instructions for new users.

Working on QGraphicsView-based local waypoints interface supporting drag-and-drop, commented code, fixed Google Maps interface, added mouse and SpinBox zoom to HSIWidget, fixed MAV-based coloring and stylesheets - MEGA COMMIT

Significantly improved plotting, now capturing data in linechart allows limmediate processing / analysis of the whole flight

Major cleanup of MainWindow constructor. All widgets have now the visible property set to false on its constructor

Improved runtime performance, currently hunting down a bug where the whole application gets repainted although only parts of it are refreshed