server: Docker expects to be run from the repository root

[s-heppner]

Currently, the server docker containers all expect to be run from the mono-repository root:

docker build -t basyx-python-server -f Dockerfile ../../..

(where ../../.. is the repository root).
This functional, but arguably somewhat ugly.

Let's discuss the possibility to change this, for example to the ./server directory.
Nevertheless, we should research how other projects do this.

[s-heppner]

This may be outdated, but should be double checked when fixing #459