Perform nightly builds of the docker image

[BenjaminRodenberg]

Depends on precice/precice#1115. As soon as this upstream issue is solved, we should create precice/python-bindings:develop on a nightly basis.

[BenjaminRodenberg]

Solving this issue will mostly revert the quickfix introduced in #130.

[BenjaminRodenberg]

I also used the quickfix from #130 in #171

[BenjaminRodenberg]

Decided to not maintain the Docker image anymore and instead rely on using pip and venv. I will take care of this in #228. Closing this issue.