Adding asdot notation to ASN views

Adds custom property to asn model to compute asdot notation if required.
Updates asn view to show asdot notation if one exists in the format xxxxx (yyy.yyy)
Adds a custom column renderer to asn table to display asdot notation if one exists

netbox/ipam/models/ip.py

@@ -130,6 +130,14 @@ class ASN(PrimaryModel):
     def get_absolute_url(self):
         return reverse('ipam:asn', args=[self.pk])
 
+    @property
+    def asdot_notation(self):
+        # Return asdot notation for an ASN larger than 65535
+        if self.asn > 65535:
+            return '{}.{}'.format(self.asn // 65536, self.asn % 65536)
+        else:
+            return None
+
 
 @extras_features('custom_fields', 'custom_links', 'export_templates', 'tags', 'webhooks')
 class Aggregate(GetAvailablePrefixesMixin, PrimaryModel):