Update to mysql plugin 2.0.0

This updates the module to install and configure the 2.0.0 version of the new relic agent. The new configuration file format and config file names are handled correctly. 

In addition, the service now creates the pidfile as root but puts the pid in it as the user running the service, because the $! variable wasn't being populated correctly outside of the su environment. I've only tested that change for the mysql new relic plugin. It shouldn't break the others but ought to be tested. This has only been tested on ubuntu 12.04.