Improve highlight_attach.cpp from http://wiki.znc.in/Highlightattach

There were a few issues I had with this, and thus I improved them.
  No customisation option for your highlight name,
   To tackle this problem, setname and getname are commands now.

  It joined the channel immediately - disrupting ongoing conversation.
   To tackle this problem, the module sends you a message now. Meaning you must
manually join the channel.

  I didn't want to be highlighted on actions or notices.
  It is unlikely someone will mention your name in a channel message without attempting to spam of some sort.
    We simply get notified per message now.