Build a UI for system settings and control

[orenskl]

Alongside the Mopidy-Iris UI there needs to be a user friendly way of setting the following things:

• Audio output device
• Enable / Disable streaming services
• Control network interfaces ( Wired / Wireless, hostname etc.)
• Provide system information (CPU, Mem etc.)

Maybe this needs to be spliced to different issues

[orenskl]

This is closed since it is a big issue, I will split it to several small ones