+MainMenue: Create new Stage files via UI +StageStatic: differentiate between developing and playing

+Added Scenes: MainMenue, LoadingScreen +Stage: Save-Load fuctionality +Sorted Prefabs and Scripts Folder

misc: just PointerGadeget snaps on tree-roof, used 'IsApproximatelyParallel' for RayFact Equivalency

+added Lot&Pendulum-Tool +Using Math3d lib for VectorCalculus +Changed Fact managment (unstable\!) +Misc refactoring

Refactored angle-prefab: Building Circle-Segment (used as the angle-representation) from Script now, using Mesh-API. Now angles > 90 degrees look much better (are not stretched or compressed in an ugly way), and potentially also angles > 180 degrees could be measured.