WIP on the sandboxing using docker.

Also created a vagrant config and provisioning rules using ansible.
Ignore the files in the sandbox
Sandboxing based on docker.

Still WIP currently in a state of proof of concept. Still needs more testing.
Adjust the vagrant config.

Fix the Dockerfile to ignore some of the folders in the project.

Various fixes of the grader, which allows it to run python and Java code.
Run the tests with a non-root user.

Also limit the number of processes a source can create.

Group the sandboxed processes into a separate process group, so that they can be killed together.
Refactored the process monitoring script to use a class, which makes the code much more readable and maintainable.
Handle call to RProcFS and the process is already collected
Ansible playbooks for deploying the grader
Some final adjustments to the ansible playbooks