dhb The changes in this commit are to make the right click in the page selector

dhb  The changes in this commit are to make the right click in the page selector
     more context sensitive.  The intent is to have a menu popup describing the
     window that will be docked or undocked and whether it will be docked or
     undocked.  This works by using treeItemChanged as a slot from the signal
     currentItemChanged from the treeWidget.  After this, we now have the choice
     of removing the virtual functions in the pages class for click and double
     click.

git-svn-id: https://bacula.svn.sourceforge.net/svnroot/bacula/trunk@4522 91ce42f0-d328-0410-95d8-f526ca767f89