A couple of fixes and little more flexibility for graphite plugin

Hi,

I have added dependency for stdlib as file_line is not part of puppet's core, so the dependency can be properly parsed by modules installers. I have also fixed the collectd::plugin::irq test as it was using "interfaces" parameter instead of "irqs".

And finally, I have added storerates and port parameters to graphite plugin.

Cheers,
Sergio.