[Long term] Guest-wifi access and traffic management

[hyojoonkim]

1. Enable open guest-wifi access. Motivation is to give easy access to house guests, also to support "Open Wireless Movement" (e.g., https://openwireless.org/),
2. However, house admin would want to ensure that house members get a guaranteed bandwidth any time, even in the event of the guest trying to hog the network with overwhelming traffic. Rate limiting on certain slice of the network (e.g., guest-vlan) would be a great feature to have. Doing some sort of QoS on multiple slices on the home network is desirable.