Add initial avatar support

We change the code for dealing with contacts quite significantly,
adding a new class, CallsBestMatch, in order to encapsulate a lot of
the functionality that was in CallsCallRecordRow.

At present avatars are not rounded and there are no auto-generated
avatars for contacts with no avatar.  This work is awaiting discussion
of Apps_Issues#164.

src/calls-contacts.h

@@ -25,7 +25,7 @@
 #ifndef CALLS_CONTACTS_H__
 #define CALLS_CONTACTS_H__
 
-#include "calls-vala.h"
+#include "calls-best-match.h"
 
 #include <glib-object.h>
 #include <libebook-contacts/libebook-contacts.h>
@@ -38,7 +38,7 @@ G_BEGIN_DECLS
 G_DECLARE_FINAL_TYPE (CallsContacts, calls_contacts, CALLS, CONTACTS, GObject);
 
 CallsContacts *      calls_contacts_new                 ();
-CallsBestMatchView * calls_contacts_lookup_phone_number (CallsContacts *self,
+CallsBestMatch *     calls_contacts_lookup_phone_number (CallsContacts *self,
                                                          EPhoneNumber  *number);
 
 G_END_DECLS