Add creating a segment using mouse
    
    Create new semicircles around the node after mouseover. These work as buttons
    to create arrow and after clicking on another node the Add topology segment dialog
    is opened. Also selecting segment works, if the segment already exists then
    the segment is selected instead of opening the dialog.
    
    https://fedorahosted.org/freeipa/ticket/5648
    
    Reviewed-By: Petr Vobornik <pvoborni@redhat.com>