Add new pre-installed services to the example: portainer, swarmprom and ELK

[thomvaill]

Those services should be pre-installed in the example so it's quicker to bootstrap a project:

• portainer for Swarm management, RBAC, API...
• swarmprom for the monitoring
• ELK for logs management

However, those services require persistent storage. So we are blocked by #3.

[thomvaill]

We should also add this project for CRON jobs: https://github.com/crazy-max/swarm-cronjob