Various improvements on distribution list management

In the window of managing a distribution list the user can get confused and use the delete button to delete an email from the list and by mistake delete the entire list.

To avoid this I suggest these 3 changes:

1) the label that appears with the mouse over change it from "Delete" to "Delete list" (see image "delete_list.png")

2) in the deletion confirmation add "Confirm deletion of the list ?" (see image "confirm-delete.png")

3) add the trash can symbol in the row of each email address to help the user understand how to delete the single contact and not the entire list