[ci skip] update Raycast documentation
[ci skip] update Raycast documentation

clarification that set_cast_to needs LOCAL point
and get_collision_point gives GLOBAL point

(cherry picked from commit 1445553fea268104bf7012785536c4e7c9c6b1e6)

pixelpicosean/my-godot-2.1,pixelpicosean/my-godot-2.1,pixelpicosean/my-godot-2.1,pixelpicosean/my-godot-2.1,pixelpicosean/my-godot-2.1