Add DeviceInfo class

DeviceInfo contains all the properties we need to instantiate a Device: id, name, type, cert, capabilities and protocol version. Before, we had a mix of passing those around as arguments or passing identity packets (ie: json). This simplifies the Device class quite a bit.

Now, BaseLink subclasses need to implement the getDeviceInfo() interface that returns a DeviceInfo, which is what we will pass around and eventually use to instantiate a Device.

This means that identity packets are an implementation detail of the LanLinkProvider and that other implementations could get the DeviceInfo in a different way.

In a future, we can add a mechanism for links to notify when their DeviceInfo changed. This will allow us to better support device renames (which now are implemented by reconnecting to the device and don't always work) or sending the capabilities fields later in the case of MacOS/iOS where we can't send them in a UDP packet due to the size limit of 1500 bytes.