Adrien Béraud authored May 24, 2017 and Guillaume Roguez committed May 30, 2017

Currently the dring API provides no way to simply
remove a contact without banning it.

This adds a ban flag to removeContact.
If set to true, the behavior stays the same and
the contact will be banned.
If set to false, the contact will be removed from the
contact list.
After the call, it won't be neither added or banned.

In both cases the ContactRemoved signal is emitted if
the contact status changes.

Change-Id: I95510f6db767b7b0e7fe15e8405b39b0bc3dd594
Reviewed-by: Guillaume Roguez <guillaume.roguez@savoirfairelinux.com>