allow only one program or diffusion for pages;

in cms.signals, manage cases when Diffusion.initial is set/changed &
clean up;

fix bug in loglist nav when max_age is 0 (no limit);

work on design for date lists;

fix bug in player on item removal;

aircox/models.py

@@ -922,7 +922,7 @@ class Diffusion(models.Model):
             return super().save(*args, **kwargs)
 
         if self.initial:
-            # force link to the top initial diffusion
+            # force link to the first diffusion
             if self.initial.initial:
                 self.initial = self.initial.initial
             self.program = self.initial.program