Remove current vagrant box and replace by nix environment

[ElectricMaxxx]

@fpletz here i would wish to get a nix environment to test and run our sandbox. it should contain all stuff mentioned on README.md. So:

• webserver to serve a syfmoyn app (nginx + php-fpm + modules)
• mysql db with credentials (+Grants) mentioned in parameters.yml for dbal implementation
• jackrabit server for jackrabit implementation
• setup script to install dbal or jackrabit implementation

[fpletz]

For this case we would need a NixOS machine because we have to manage multiple services. Either using vagrant and the nixos provider or with nixops (can deploy to i.e. virtualbox).