Local::Roster: Removed useless component.

That component is not used anymore. Local contacts are now handled by
the Opal component following the account type.
TODO: Updated.
Call History View: Renamed active_contact variable.
Opal Roster: Fixed popup menus not being displayed.

UI popups were not displayed when invoking roster menus.
This was due:
 - a missing "questions" connection between presentities and heaps;
 - a confusion between "questions" objects due to multiple inheritance
   from LiveObject with the new design. We have several questions to
   relay following we are a Cluster or a Bank. Clusters will relay
   questions from Heaps. Banks will relay questions from Accounts.
PresenceCore: Turn it into an URIActionProviderStore.

This allows the Opal CallManager to add Actions to the PresenceCore.
Roster: Started moving Presentities and Roster to the new Action stuff.