Also return correct status codes.

Allow enabling and disabling of firewall via POST method as well as GET.
(I recommend disabling GET when all clients have been updated)

Refactored FirewallResource class into multiple smaller classes to make
URL routing clearer.

Add in firewall again. Fixed an issue where all packets would be dropped if a rule could not be found. Also fixed an issue where all-zero MAC addresses would be used as a match for wildcarded MACs in some cases.