Change copyright notice to short form

apps/calendar/ajax/activation.php

apps/calendar/ajax/changeview.php

apps/calendar/ajax/choosecalendar.php

apps/calendar/ajax/createcalendar.php

apps/calendar/ajax/editcalendar.php

apps/calendar/ajax/editevent.php

apps/calendar/ajax/editeventform.php

apps/calendar/ajax/getcal.php

apps/calendar/ajax/geteventinfo.php

apps/calendar/ajax/newcalendar.php

apps/calendar/ajax/newevent.php

apps/calendar/ajax/neweventform.php

apps/calendar/ajax/settimezone.php

apps/calendar/ajax/updatecalendar.php

apps/calendar/caldav.php

apps/calendar/css/style.css

apps/calendar/export.php

apps/calendar/index.php

apps/calendar/js/calendar.js

apps/calendar/lib/calendar.php