the previously deleted set proxy from JGitUtil was just...meh

This checks if we got a proxy set in the properties file
Additionally the user can provide a list of not-proxy hosts.
This setup will then check, if a proxy is available and if so,
make sure it only gets used if the uri is not on the not-proxy list.

Moodle needs this structure to read the information to show.
What model to finally agree on has to be discussed later

this component initializes an DockerClient on startup,
then provides a method to run an container with an given image String
and n given Bind-mounts.
This method waits for this container to finish before returning,
so don't call any services that should just be started and left alone!

For this the library github-java-docker is used:
https://github.com/docker-java/docker-java

For this to work, the container this is run in obviously needs
access to the docker socket

- defined modocot URI for unittests and submissions
- directly expect a textfile, not an archive
- store config file and local repo copy in persistent place,
    instead of using Gitea

BREAKING CHANGE: file to be uploaded changed from zip to text
BREAKING CHANGE: no longer uses Gitea

- removed proxy setup method
- reworked clone method

BREAKING CHANGE: method signature for cloneRepository changed