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
@yasn77 From having a brief look at a few other gds-operations repos we have, the Rakefiles seem fairly consistent in that they don't enforce the disabling of the 80char limit, despite the fact that it's against the Puppet styleguide. Whilst I agree, in principle, that this module (and all of our others) should follow the styleguide, I think it makes more sense right now to make them all match, and we can then look to disable them all in every repo afterwards if we need to.

Ultimately, this shouldn't be a blocker to merging, though - more a passing comment on the fact that we're a bit out of sync in our usage here.