Router-DAO Address Exchange

[asoltys]

This pull modifies the existing Subnet DAO selection component to make it so that only a single DAO can be joined at a time and provides a mechanism for the router dashboard to exchange information about the ethereum contract address, wallet address, and mesh IP address with the Aragon UI.

The exchange is a two-step process and the order of the steps doesn't matter:

• The router's ethereum wallet address is encoded as a QR code to be scanned by the subnet DAO organizer into the Aragon app.
• The router scans the assigned mesh IP address and the ethereum address of the DAO contract from a QR code generated by the Aragon app.

When the QR code is scanned, the router takes the /64 subnet IP address that was generated and assigns itself the first /128 address in the range as its mesh IP.

Because setting the mesh IP address of the router requires rita to restart, a countdown dialog is displayed to let the user know that rita is unavailable and will hopefully be back soon.

Fixes #30 and #32

[asoltys]

rebased on master and fixed an issue with the countdown timer not being cleared properly