Add the possibility to bind an address on Discovery instead of a device

[bl0ggy]

Add the possibility to bind an address on Discovery instead of a device, in case a device has multiple aliases. Because of address binding we need to know which alias received the camera, so we now send a remote and a local info in Discovery.emit('device'). This breaks backward compatibility though

The urn has been remvoved from the Cam constructor in a previous while it is set in discovery.js The urn is important to compare cameras, so I added it back.

[coveralls]

Coverage decreased (-0.05%) to 87.259% when pulling 256e82ff358aa20a00fa7519bf2c482a705fb1e7 on bl0ggy:bind_local_address into 2a7f9fe267058e8d069253f7d1189e5744b09470 on agsh:master.