Create subscription mechanism for OSC

[hamoid]

This would avoid hardcoding the ip address of someone who wants to receive OSC messages.

That's how https://github.com/sebpiq/rhizome works, by subscribing to messages.

So the server receives an OSC message like "I'm here, interested in OSC", and the server then adds the ip address of whoever sent that message to a oscTargets array, which is later used for forwarding messages.