Refactored Node3D rotation modes

* Made the Basis euler orders indexed via enum.
* Node3D has a new rotation_order property to choose Euler rotation order.
* Node3D has also a rotation_mode property to choose between Euler, Quaternion and Basis

Exposing these modes as well as the order makes Godot a lot friendlier for animators, which can choose the best way to interpolate rotations.
The new *Basis* mode makes the (exposed) transform property obsolete, so it was removed (can still be accessed by code of course).

scene/3d/camera_3d.cpp

@@ -71,6 +71,8 @@ void Camera3D::_validate_property(PropertyInfo &p_property) const {
 			p_property.usage = PROPERTY_USAGE_NOEDITOR;
 		}
 	}
+
+	Node3D::_validate_property(p_property);
 }
 
 void Camera3D::_update_camera() {