Add helpdesk role/app

[artcz]

We need to be able to set up our helpdesk app too.. Whichever app that's going to be for 2019.

[alexsavio]

It's also included in the revenant repo. And I am working on porting the configs to Ansible in the epcon-apps role: https://github.com/EuroPython/ep-config/pull/15/files#diff-c6acb7464d380b381cc5146aeedb8455