Fix XEP-0191 implementation

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Contact: include blocked status

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Block/unblock menu item (#134)

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>
Block/unblock: wait for IQ response and update UsersProvider

Signed-off-by: Daniele Ricci <daniele.athome@gmail.com>