Fixed problem in case an absences has multiple cases. Use the minimum as this is the first one

Signed-off-by: Malte Sussdorff <malte.sussdorff@cognovis.com>
Made sure that we only display active vacations in the cube, unless a different status was selected. Otherwise this is confusing for the user especially with deleted absences.

Signed-off-by: Malte Sussdorff <malte.sussdorff@cognovis.com>
Added support for permission checks on viewing absences

Signed-off-by: Malte Sussdorff <malte.sussdorff@cognovis.com>