Wrap long lines in NSE (>200 columns)

Mostly in documentation (the description field, for instance), but also
some long literal strings. Lua 5.2 introduces a string escape, "\z",
which escapes any amount of subsequent whitespace, including newlines.
This can be used to wrap string literals without upsetting indentation.
http://www.lua.org/manual/5.2/manual.html#3.1
Remove useless calls to string.format

stdnse.print_debug accepts a format string and arguments, making
string.format redundant in calls of this form:

stdnse.print_debug(1, string.format("%s: error", SCRIPT_NAME))
stdnse.print_debug(("length %d"):format(#tab))

These can be rewritten as:

stdnse.print_debug(1, "%s: error", SCRIPT_NAME)
stdnse.print_debug("length %d", #tab)