NSE re-categorization

* Merge the "backdoor" category into "malware"
* Add "auth" for authentication credential determination
* Rename "vulnerability" to "vuln"
* Place 12 scripts into their correct categories

scripts/bruteTelnet.nse

@@ -2,7 +2,7 @@ id='bruteforce'
 author = 'Eddie Bell <ejlbell@gmail.com>'
 description='brute force telnet login credientials'
 license = 'Same as Nmap--See http://nmap.org/book/man-legal.html'
-categories = {'vulnerability'}
+categories = {'auth', 'intrusive'}
 
 require('shortport')
 require('stdnse')