Do not create two menu items in applications menu

[Frederik Himpe]

Screenlets creates two menu items in my applications menu: one to start the screenlets manager, and another one to start the screenlets daemon. The latter should be dropped, because it is possible to start the daemon from the manager application. A separate menu item for starting the daemon, is not important, because users will only need to do this seldomly (on first use): in a normal use case, the daemon will be started by the desktop's session manager. The manager application can appear in GNOME's Preferences menu then. This helps reducing menu clutter.