title: Move all subviews to container view keeping positions and constraints
body: <p>I'm using Xcode 5 and autolayout in my project. I have a <code>.xib</code> file with a lot of subviews and constraints between them. Now I need to create an intermediate fullscreen container view and put all subviews there. So now I have <code>view-&gt;subviews</code>, and I want <code>view-&gt;container view-&gt;subviews</code>. When I do this in IB by dragging subviews into container view, they all get centred and all constraints get lost. It's going to be a little hard to restore all constraints manually. Is there a smart way to do this keeping all subviews' positions and constraints?</p>