add ok-button to datetime picker

Signed-off-by: Felix Nüsse <felix.nuesse@t-online.de>

fix lint issues

Signed-off-by: Felix Nüsse <felix.nuesse@t-online.de>

use confirm (like contacts-app)

Signed-off-by: Felix Nüsse <felix.nuesse@t-online.de>

add margin to buttons for timepicker

Signed-off-by: Felix Nüsse <felix.nuesse@t-online.de>

remove margin for ok-button

Signed-off-by: Felix Nüsse <felix.nuesse@t-online.de>