Added support for NFS3 statistics

[David Andruczyk]

I have added support for NFS3 client statistics. and a pull request has been sent to the percona account on github. Until it's merged (or rejected) users can try it out via my fork at:

https://github.com/djandruczyk/percona-monitoring-plugins/tree/nfs3

Clone my repo and checkout the "nfs3" branch, run "make.sh nodocs"
 the scripts and templates will be in the release/percona-monitoring-plugins-1.1.5/cacti subdir (scripts and templates respectively)

Copy the ss_get_by_ssh.php script to /usr/share/cacti/scripts, import the cacti_host_template_percona_nfs3_server_ht_0.8.6i-sver1.1.5.xml template.

The begin graphing NFS3 client stats, select your device in cacti, change it's type to "Percona NFS3 CLient HT", save it, then select "Create graphs for this host" and select the "Percona NFS3 Client Operations GT" and click on "create".

[Roman Vynar (roman-vynar)]

Discussion here https://github.com/percona/percona-monitoring-plugins/pull/11