fix crash with timingdiagram
followup pull #119, cmake out of tree

While building out of tree it complains about the missing ui_*.h header.
Headers are being created on the build/binary directory.
move xpm definition to qucs
move addTab to qucs
move scrollview changed connect to qucsapp
move delete from tab to qucsapp
position label change to signal slot
replace undo,redo with signal slot
move filechanged to signal/slot
move change filename to signal slot