Steps to reproduce
create contact
create group
add contact to group
open group
select contact
click on delete contact

Actual results
If one deletes a contact from any group, it is automatically deleted from all groups and the adressbook

Expected results
Deleting a contact from a group is probably interpreted as removing it from this specific group without an influence on any other group. By pressing the delete button the user should hence receive a warning, that his action will lead to deleting the contact from of all groups and his address book.