Add common logic for xref buttons, links when viewing object

about dang time for this..probaby needs improvement but a good start

tailbone/views/master.py

@@ -2502,8 +2502,23 @@ class MasterView(View):
         """
         Method stub, so subclass can always invoke super() for it.
         """
+        obj = kwargs['instance']
+        kwargs['xref_buttons'] = self.get_xref_buttons(obj)
+        kwargs['xref_links'] = self.get_xref_links(obj)
         return kwargs
 
+    def get_xref_buttons(self, obj):
+        buttons = []
+        for supp in self.iter_view_supplements():
+            buttons.extend(supp.get_xref_buttons(obj))
+        return buttons
+
+    def get_xref_links(self, obj):
+        links = []
+        for supp in self.iter_view_supplements():
+            links.extend(supp.get_xref_links(obj))
+        return links
+
     def template_kwargs_edit(self, **kwargs):
         """
         Method stub, so subclass can always invoke super() for it.
@@ -5062,10 +5077,8 @@ class ViewSupplement(object):
 
     def __init__(self, master):
         self.master = master
-
-    @property
-    def model(self):
-        return self.master.model
+        self.request = master.request
+        self.model = master.model
 
     def get_grid_query(self, query):
         """
@@ -5111,6 +5124,12 @@ class ViewSupplement(object):
         renderers, default values etc. for them.
         """
 
+    def get_xref_buttons(self, obj):
+        return []
+
+    def get_xref_links(self, obj):
+        return []
+
     def get_version_child_classes(self):
         """
         Return a list of additional "version child classes" which are