Support for Dynamic BVH as 2D Physics broadphase

List of changes:
- Modified bvh class to handle 2D and 3D as a template
- Changes in Rect2, Vector2, Vector3 interface to uniformize template
calls
- New option in Project Settings to enable BVH for 2D Physics (enabled
by default like in 3D)

core/math/vector3.cpp

@@ -54,15 +54,6 @@ real_t Vector3::get_axis(int p_axis) const {
 	return operator[](p_axis);
 }
 
-int Vector3::min_axis() const {
-
-	return x < y ? (x < z ? 0 : 2) : (y < z ? 1 : 2);
-}
-int Vector3::max_axis() const {
-
-	return x < y ? (y < z ? 2 : 1) : (x < z ? 2 : 0);
-}
-
 void Vector3::snap(Vector3 p_val) {
 
 	x = Math::stepify(x, p_val.x);