-Scene edit state is saved outside the scene now, to avoid changes .tscn files when nothing really changed
-Created a VariantWriter helper to unify all variant to text writing
-Moved SceneFormatText writing to VariantWriter
-Moved ConfigFile to use VariantWriter and VariantParser, added compatibility mode for old .cfg files that use engine.cfg format
-Added Navigation & NavigationPolygon nodes
-Added corresponding visual editor
-New pathfinding algorithm is modern and fast!
-Similar API to 3D Pathfinding (more coherent)