Add GDS Verify module changes

GDS Verify(IDA) project use a fork of this graphite module. It seems like a good idea to incorporate changes in to this module, with the view the Verify project dropping the fork and using only this module.

The GDS Verify additional changes are:
 - Ability to specify the user used to run the processes
 - Install from Debian package
 - Some carbon cache options
@annashipman When changing the user of the running process in the upstart conf file, the process has to have stopped before upstarts rereads the config. So setting `hasrestart` to `true`, will prevent a change to the user ever being detected.