[clipboard] Event definition

Hi Hallvord,

At 
<http://dev.w3.org/2006/webapi/clipops/clipops.html#clipboard-event-interface>, 
a reference to DOM *2* Events is made; it should be updated.

Also, the initClipboardEvent method should be removed in favour of a 
constructor, as described at 
<http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#constructing-events>.

HTH
Ms2ger