change path when objects get moved

[frisi]

we store the objects path in the mustread records to be able to filter for records within a certain context.

when an objects gets moved in the plonesite, existing mustread records have invalid path information.

we should consider to register a subscriber for objectemovedevent, that looks up records for the object uid and changes the path to the new location of the object.
(and or provide a cleanup utility function that checks for records with invalid paths and fixes them)