Proposed solution for issue 2565: Provide magic menu checkbox for pasting magics instead of direct executing

This is related to issue #2565 (https://github.com/ipython/ipython/issues/2565).           
There is no reasonable way to programmatically distinguish between magics with parameters  and magics that do not require params.                                                     
Thus, I have implemented "Only Paste Magics" menu checkbox. When checked menu items will just paste magics into the input without executing them. When unchecked (default) magics are executed.