Add command interface to ConfServ on 2nd port + tests

Implemented commands:
- add_tag = add a new tag to configurations list for a given agent
- rem_tag = remove a tag from configurations list for a given agent
- dump_file = dump current state in memory of the configurations list either to a selected filepath or to same filename plus current date and time

Planned (non-implemented) commands:
- dump_db = dump current state in memory of the configurations list to the database, to be available only when using a DB as input