Improve changing positions of members #154
Description
Due to the change to keep the history of roles of volunteers "changing" a position became a bit more work for team leaders. Right now an end date needs to be set for the current "team member", and then a new "team member" for the same volunteer needs to be created.
It would be great if there is a "change position" button in the edit screen of a member, in which you can select the new position. When saving the current position is automatically being archived and a new one for the new position will be created, by using the current date as end date for the old position and as start date for the new positon.