implements banned account, add a tab at the end of account details
that shows a list of banned contacts, and on click displays a pannel
with detailed contact informations, providing the option to deban
this contact.

Change-Id: Icc2a0e315830bc3f7beb23797bedf12ecfd9a074
Reviewed-by: Anthony Léonard <anthony.leonard@savoirfairelinux.com>