Add GDS Verify module changes

__* PR #31 was originally opened to merge GDS Verify changes in to this module. After some comments, I thought it best to close PR #31 and create a new branch with cherry picked changes. Hopefully this should be a bit clearer than one big commit (as is the case in the original PR) *__

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
Your comment in Slack is completely correct - github blame is different to git blame ;)

```
[gds/puppet-graphite:yasn77-idap_gds_merge●]$ git status
On branch yasn77-idap_gds_merge
Your branch is up-to-date with 'yasn77/idap_gds_merge'.

nothing to commit, working directory clean
[gds/puppet-graphite:yasn77-idap_gds_merge●]$ git blame manifests/service.pp | grep hasrestart
b020c382 (Yasser Nabi      2014-12-03 17:02:16 +0000 14)     hasrestart => false,
5df15dd1 (Yasser Nabi      2014-10-23 18:32:15 +0100 20)     hasrestart => false,
5df15dd1 (Yasser Nabi      2014-10-23 18:32:15 +0100 27)     hasrestart => false,
```