The main goal of this patch is to be able to recover ContactMethods
and conversations which have not been added to the users's contacts
and/or which have no call history. This happens in the case that the
users only sends chat messages to a ContactMethod.

Note that there is a possibility for more than one file to be
associated with the same CM, in the case the sha1 of that CM has
changed (eg: a contact UID has been associated with the CM at some
point). In this case, the most recent recording is used. However,
this is a problem which already exists and is unrelated to this patch.

Tuleap: #270
Change-Id: I5c67be83028af3fc3e1950909574ec947c55c50c