Missing strings in the Birthday plugin.  (Birthday-Admin.english.php)

Signed-off-by: Sven Rissmann <creaworld-media@gmx.de>
German translation for calendar plugin

Signed-off-by: Sven Rissmann <creaworld-media@gmx.de>
German translation for plugin contact page

Signed-off-by: Sven Rissmann <creaworld-media@gmx.de>
German translation for plugin edit_history

Signed-off-by: Sven Rissmann <creaworld-media@gmx.de>
German translation for plugin mass_attach.

Signed-off-by: Sven Rissmann <creaworld-media@gmx.de>
German translation for plugin mentions

Signed-off-by: Sven Rissmann <creaworld-media@gmx.de>
German translation for plugin skin_selector.

Signed-off-by: Sven Rissmann <creaworld-media@gmx.de>
German translation for plugin users_online_today.

Signed-off-by: Sven Rissmann <creaworld-media@gmx.de>