Normalize NSEDoc documentation of scripts.

I made every script follow a standard form: it starts with the id, followed by
the description. The description is contained in [[ ]] delimiters. The
description is in the global description variable, not in a LuaDoc comment.
Other LuaDoc information such as @args and @usage follows the description in a
comment.

The first paragraph of each description is a a short summary of what the script
does. More detailed information, if any, is given in following paragraphs.

I also improved some wording and formatting in a few cases.

scripts/ircServerInfo.nse

@@ -1,6 +1,12 @@
---- Gather information from an IRC server. It uses STATS, LUSERS, and other
--- queries to obtain this information.
---@output
+id = "IRC Server Info"
+description = [[
+Gathers information from an IRC server.
+\n\n
+It uses STATS, LUSERS, and other queries to obtain this information.
+]]
+
+---
+-- @output
 -- 6665/tcp open     irc\n
 -- |  IRC Server Info: Server: foo.bar.net\n
 -- |  Version: hyperion-1.0.2b(381). foo.bar.net \n
@@ -9,10 +15,6 @@
 -- |  Source host: bar.foo.net\n
 -- |_ Source ident: OK n=nmap\n
 
-id = "IRC Server Info"
-
-description = "Gets information from an IRC server by issuing STATS, LUSERS, etc queries."
-
 author = "Doug Hoyte"
 
 license = "Same as Nmap--See http://nmap.org/book/man-legal.html"