applet: configure notification source

The desktop file will be installed to /usr/share/applications. All
destkop files in the applications directory are displayed in user menus
but abrt-applet is not intended to be started by users. Therefore
NoDisplay entry is used to prevent displaying applet in the
menus.

Related to rhbz#994009

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Signed-off-by: Richard Marko <rmarko@redhat.com>
spec: install applet's desktop file to system dir

Closes rhbz#994009

Signed-off-by: Jakub Filak <jfilak@redhat.com>
Signed-off-by: Richard Marko <rmarko@redhat.com>