KinematicBody split between new CharacterBody and PhysicsBody

PhysicsBody now has methods move_and_collide/test_move and needed
properties for these methods: safe margin, locked axes (3D only).

Moved collision_exceptions from StaticBody to PhysicsBody for 3D
(same as 2D, and conforms to documentation).

RigidBody doesn't have test_motion method anymore, it's now redundant
with PhysicsBody.test_move.

scene/2d/collision_object_2d.cpp

@@ -408,6 +408,10 @@ void CollisionObject2D::set_only_update_transform_changes(bool p_enable) {
 	only_update_transform_changes = p_enable;
 }
 
+bool CollisionObject2D::is_only_update_transform_changes_enabled() const {
+	return only_update_transform_changes;
+}
+
 void CollisionObject2D::_update_pickable() {
 	if (!is_inside_tree()) {
 		return;