[Week view] Show only group members

If the selected item is a group, only the group members should be shown on right side.

changed milestone to %1.0a1

added part::frontend prio::1 type::bug labels

added source::customer label

assigned to @hansegucker

created merge request !67 (merged) to address this issue

mentioned in merge request !67 (merged)

closed via merge request !67 (merged)

mentioned in commit 2e023399