documentation for local installation and small fixes

• documentation on how to install and configure a local cluster (without the 'what it does' section for now)
• beginning of the documentation for experimenting with autograding homeworks (screen captures)
• makefile fixes :
• bind localhost to moodle in /etc/hosts.
• start the minikube local cluster with cpus=4.
• patch to kustomization.yaml local configuration: reduce the number of cores for the autograde-service from 2 to 1.

Closes #72 (closed)