Reinstate the dev vm - Githubissues

The dev vm was no longer functioning as intended. This PR fixes the following problems:

GMP extension is installed during provisioning
Several ansible dependency installation issues have been resolved
The default IP address used by the VM was changed to prevent collision with Stepup-VM
Worked around the incorect setting of the default locale in the dev vm (might need work later)

PlantUML was removed from the project.

The readme was updated.

OpenConext / Stepup-tiqr