Rewrite of haproxy-sessions-by-servers

Rewrite of haproxy-sessions-by-servers to better mimic the other plugins.  I believe the purpose of this plugin was to show the number of active sessions by member server.  That wasn't occuring and this plugin was broken upon symlink.

I also added the ability to parse both URL and Socket stats.

Tested in our clq.it production environment, and verified working for socket stats.

For questions, please notify allan.parsons@gmail.com.