merge Georgs calendar

apps/calendar/ajax/ajax.php

apps/calendar/appinfo/app.php

apps/calendar/appinfo/database.xml

apps/calendar/appinfo/info.xml

apps/calendar/caldav.php

apps/calendar/cfg/root.cfg.php

apps/calendar/css/style.css

apps/calendar/img/icon.png

apps/calendar/index.php

apps/calendar/install.php

apps/calendar/js/calendar.js

apps/calendar/js/calendar_dialog.js

apps/calendar/js/calendar_init.js

apps/calendar/lib/PDO.php

apps/calendar/lib/calendar.php

apps/calendar/lib/hooks.php

apps/calendar/libs/iCalcreator.php

apps/calendar/libs/oc_calendar.php

apps/calendar/libs/sanitize.php

apps/calendar/settings.php