add examples for using Property message; make accesser.Value.set to clear other fields; attach Property message to Modification and Action
add explanation to usage of Action message
add filter_properties_by_name_chain and entity_has_name_chain function and ut; rename to use name_chain for other functions as well
do_modification and ut checkin (nice!)
add logic so no new entity is created by do_modification is the entity_id is already in use
do_action and ut checkin