config: Update reference keys

Issue: 4974

1. Use https instead of http everywhere
2. Organize and annotate references by
    - Referenced by ET/Open and ET/Pro
        - URL resolves and works as intended (to provide supplemental
          information regarding a reference value, e.g., bug id, cve
          value)
        - URL no longer resolves
        - URL resolves but doesn't work as intended (to provide
          supplemental information)
    - Not referenced by ET/Open nor ET/Pro
        - URL resolves and works as intended (to provide supplemental
          information regarding a reference value, e.g., bug id, cve
          value)
        - URL no longer resolves
        - URL resolves but doesn't work as intended (to provide
          supplemental information)

etc/reference.config

@@ -1,26 +1,44 @@
 # config reference: system URL
 
-config reference: bugtraq   http://www.securityfocus.com/bid/
-config reference: bid	    http://www.securityfocus.com/bid/
-config reference: cve       http://cve.mitre.org/cgi-bin/cvename.cgi?name=
-#config reference: cve       http://cvedetails.com/cve/
-config reference: secunia   http://www.secunia.com/advisories/
+#
+# Note: https// used
+##############################
+# Referenced by ET/Open ET/Pro
+##############################
+
+#  resolves, works as intended
+config reference: cve       https://cve.mitre.org/cgi-bin/cvename.cgi?name=
+config reference: nessus    https://www.tenable.com/plugins/nessus/
+config reference: url       https://
 
 #whitehats is unfortunately gone
-config reference: arachNIDS http://www.whitehats.com/info/IDS
-
-config reference: McAfee    http://vil.nai.com/vil/content/v_
-config reference: nessus    http://cgi.nessus.org/plugins/dump.php3?id=
-config reference: url       http://
-config reference: et        http://doc.emergingthreats.net/
-config reference: etpro     http://doc.emergingthreatspro.com/
-config reference: telus     http://
+#
+#  no longer resolves
+config reference: McAfee    https://vil.nai.com/vil/content/v_
+config reference: bid	    https://www.securityfocus.com/bid/
+config reference: bugtraq   https://www.securityfocus.com/bid/
+config reference: md5	    https://www.threatexpert.com/report.aspx?md5=
+
+#  resolves, but non-useful page
+config reference: secunia   https://www.secunia.com/advisories/
+config reference: arachNIDS https://www.whitehats.com/info/IDS
+
+###################################################
+# No longer referenced from ET/Open ET/Pro rulesets
+###################################################
+
+#  resolves
+config reference: exploitdb https://www.exploit-db.com/exploits/
+config reference: msft      https://technet.microsoft.com/security/bulletin/
+
+#  resolves, but non-useful page
+config reference: et        https://doc.emergingthreats.net/
+config reference: etpro     https://doc.emergingthreatspro.com/
+config reference: telus     https://
+
+#  no longer resolves
+config reference: xforce    http://xforce.iss.net/xforce/xfdb/
 config reference: osvdb     http://osvdb.org/show/osvdb/
 config reference: threatexpert http://www.threatexpert.com/report.aspx?md5=
-config reference: md5	    http://www.threatexpert.com/report.aspx?md5=
-config reference: exploitdb http://www.exploit-db.com/exploits/
 config reference: openpacket https://www.openpacket.org/capture/grab/
 config reference: securitytracker http://securitytracker.com/id?
-config reference: secunia   http://secunia.com/advisories/
-config reference: xforce    http://xforce.iss.net/xforce/xfdb/
-config reference: msft      http://technet.microsoft.com/security/bulletin/