Create an installer script

[holtgrewe]

Is your feature request related to a problem? Please describe.
Some users don't want to go through many steps for getting a VarFish server started.

Describe the solution you'd like
We should provide a simple installer script that:

• Asks users some questions
  • desired setup with self-signed certificate/custom cert/letsencrypt
  • hostname etc.
  • auto-generate account for user-level S3 upload
  • auto-generate safe admin password
  • point to documentation where to learn more
• Performs a checkout of varfish-docker-compose
• Downloads the background data for WES/WGS

While writing this, we should double-check that the installation manual is up to date.

Describe alternatives you've considered
N/A

Additional context
N/A