Issue 409: Fix activate/deactivate

Reported by Nikolaus Schaller, Nov 5, 2012

1. if one app is activated, the currently active should be sent a 
deactivate event
2. if an app is deactivated, hide the menu and floating panels etc. 
and grey out the title bar and buttons of the windows
3. if an app is activated, show the menu and floating panels etc. 
and show the title bar and buttons

Currently,
- the menus of all apps are overlapping
- the window titles are overlapping (since we have no shadow)

Comment 1 by Nikolaus Schaller, Nov 8, 2012

If an application is closed, some other app must become the active 
one.
If this should not be done randomly but in some "stacking" 
order, maybe the window-manager (i.e. loginwindow/WorkspaceServer) 
must help to track the active apps. I.e. this must involve more DO 
and not only re-linking /.QuantumSTEP/active

mySTEP