Feature/adjustable size of mons mgrs

For non-openstack deployments it should be possible to adjust the number of mons and mgrs within the cluster. (See: #442 (closed))

---

Merge Prerequisites

• Description and title are descriptive
• Code is readable and syntactically correct
• Code is understandable
• Tests added (if needed)
• Docs updated
• Commit messages look good

As a developer: please do not tick these boxes yourself. As a reviewer: please get yourself a hot beverage.