Add --config-name to recursor

This adds --config-name to pdns_recursor and rec_control.
Changed s_programname to recursor as that makes the logic more like pdns_server and is useful.
The rec_control has been updated as well so we can still query the correct recursor
Improved error message for socketfile not found
Merge pull request #951 from cyclops1982/935

Add --config-name to recursor