IE: Right click on selected content not removes the selection.

The problem was that 'beforepaste' event was thrown when right clicking. The 'beforepaste' event was used to copy/paste content for IE. With this fix the 'beforepaste' event is not necessary any more, the whole copy/paste process is done in the 'paste' event. This solution is only for IE8 and below. For other IE versions (9 and above) the event 'beforepaste' is still needed.
Merge pull request #1137 from najor/hotfix-0.24.x-rt53267-copy-paste-ie

IE: Right click on selected content does not remove the selection.