Caldav support

(WLAN-Kabel) Missing dependency added
(WLAN-Kabel) Added caldav support
(WLAN-Kabel) Multiple calendars can be displayed in one widget
(WLAN-Kabel) Added more widget settings
(WLAN-Kabel) State structure changed
(WLAN-Kabel) Appointments are now shown in the popup
(WLAN-Kabel) Some internal functions revised
(WLAN-Kabel) Fixed an error when saving the authentication data