Rename box-definitions to match product name conventions.

I hope, I interpreted
https://wiki.mageia.org/en/Product_naming correctly. If not.
please submit a push-request.
Add Mageia-Mageia-Cauldron-Vagrant-Server-minimal-x86_64.

Based in Mageia-4-Vagrant-Server-minimal-x86_64. Since as
of today, both are quite close, onle the boot-image and
it's checksum had to be changed.
Add Mageia-Cauldron-Vagrant-Server-minimal-x86_64.

Based in Mageia-4-Vagrant-Server-minimal-x86_64. Since as
of today, both are quite close, onle the boot-image and
it's checksum had to be changed.