web: Simple network configuration.

Fixes #456.
web: Use on/off buttons for connections.
web: Collapse ignore-auto-dns network setting into method.
web: Improve network interface hardware information panel layout.
web: Throttle NetworkManager change notifications.

State changes of devices happen quite fast and only cause visual
flicker.
web: Indicate when a connection might be automatically activated.
web, NM Model: Use "priv(obj).foo" notation instead of obj[' foo'].

This is less obscure, more robust, and indeed a bug was found.

(Also, 'type' is no longer optional with get_object).
web, NM Model: Don't use the fake object manager.

This is to show what is needed to make the model work.
web, NM model: Don't ask udev for non-udev devices.
web, NM model: Restructure code to better show the individual parts.
web, networking: Allow resetting of autoconnect behavior to our default.
dbus-json: Allow working without D-Bus proxies.
web, NM model: Use a object manager but no proxies.

The proxies are not needed but the object manager helps a lot.
web: Add "method" label to IP config dialog.
web: Factor out On/Off button.
web: Expose autoconnect setting of a connection directly.
web: Test network page interaction with nmcli.