[MINOR] Add "a name" to stats page

[MINOR] Add "a name" to stats page

If you have a lot of proxies/servers in your stats page it is
not easy to locate the one you are interested in. You can
of couse use search function from you favorite web browser
but browsers often lost their focus when reloading stats.

This patch adds <a name> html tags for proxies, frontends, servers
and backends. You can use it to access a specific place, for example:

http://(stats_url)#proxy
http://(stats_url)#proxy/Frontend
http://(stats_url)#proxy/server1
http://(stats_url)#proxy/server2
http://(stats_url)#proxy/Backend