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_physics_field.py

@@ -175,7 +175,7 @@ class PHYSICS_PT_collision(PhysicButtonsPanel, bpy.types.Panel):
 
         if md:
             # remove modifier + settings
-            split.set_context_pointer("modifier", md)
+            split.context_pointer_set("modifier", md)
             split.operator("object.modifier_remove", text="Remove")
             col = split.column()