Implement Network Disabling

A feature for the sysdaemon...

Depending on the settings defined in the exam_default.cfg (for each exam) various networking capabilities are to be enabled or disabled.

At the moment the program only needs to do full network blocking. My thinking is that this will be trivial with a few iptable rules (moderated by ufw or something). However, in the future it would be nice to disable only wireless devices or enable only certain subnets etc. so some thought should be put into this.

Assuming that no periodic check is necessary you can place your code to load the iptable rules into src/modules/networking/bootstrap_tasks.py

Just a thought, but perhaps a good solution to this problem would be to load an iptable rule set from the config directory. This way when we invent a GUI for configuring exams the GUI can create a firewall rule-set similar to existing firewall UI's.