Bring back the Global Menu support, that means:

• Figure out how to use QDBusMenu stuff in our KDE Platform Theme (D3085)
• Resurrect / massively cleanup KAppMenu (acts as registrar for the applications)
• Restore application menu button in KWin and KDecoration
• Write a global menu applet

Also some other things:

• Figure our KXMLGui magic to auto-hide the menu bar
• Figure out KXMLGui magic to hide the "Show Menu bar" check box (there was a discusson on plasma or kde-devel about this for Unity)