Implemented addObj and delObj for CallControl.Extension
Relevant Issue
https://project.iopsys.eu/issues/13566
Problem
CallControl.Extension did not have addObj and delObj functions correctly implemented, as they were simple debug strings to inform us that we are unable to change the number of the Extension objects.
The functions were implemented and adding objects was tested. Factory reset with the newest .json config file now correctly creates 10 Extension entries.