use set as a suffix (matches operators)

- set_frame() --> frame_set()
 - set_context_pointer() --> context_pointer_set()

material adding works for curves and metaballs, new function to remove materials.

materials.link() didnt well fit how this is used elsewhere
 - order matters
 - it can be linked more than once.
 - remove(material), isnt that useful since you need to manage indicies.

... use list style functions instead. materials.append(mat) / materials.pop(index)

release/scripts/ui/properties_object.py

@@ -142,7 +142,7 @@ class OBJECT_PT_groups(ObjectButtonsPanel, bpy.types.Panel):
             if ob.name in group.objects:
                 col = layout.column(align=True)
 
-                col.set_context_pointer("group", group)
+                col.context_pointer_set("group", group)
 
                 row = col.box().row()
                 row.prop(group, "name", text="")