AddressBookWindow: First steps GTK3 & Ekiga::Action porting.

Menus have not be reimplemented yet.
GActorMenu: Added the possibility to name menu sections.
GmWindow: Fixed hide_on_esc property having no effect.

The window was hidden and not destroyed whatever the property value was
set to.
AddressBook: Turn Book and Source into Actors.
Evolution: Ported Contact implementation to the Actor framework.
Evolution: Ported Book to the Actor framework.
Call History: Dropped explicit Actor inheritance for Books.

This has been moved into the base class.
GmInfoBar: Added guard against empty messages.
LDAP: Ported plugin to the Actor framework.
GActorMenu: Added option to enable/disable section labels in menus.
Call History: Cleanups and optimizations.
Book View: Ported to the new Actor framework and GTK3.
Address Book: Ported to GTK3 and the new Actor framework. New design.