DNS improvements


git-svn-id: https://svn.ntop.org/svn/ntop/trunk/nDPI@7333 a02cd0c1-8e76-42e1-a119-56f9641475e2
Added DNS request type 


git-svn-id: https://svn.ntop.org/svn/ntop/trunk/nDPI@7336 a02cd0c1-8e76-42e1-a119-56f9641475e2