Port uproxy-networking to freedom 0.6

Ah...interesting. I just played around with this in the TypeScript playground. I *think* a plain-old JavaScript function declaration would be equivalent, e.g.:
```typescript
module Churn
  function filterCandidatesFromSdp (sdp:string) : string {
    return sdp.split('\n').filter((s) => {
      return s.indexOf('a=candidate') != 0;
    }).join('\n');
  }
  // ...
  // ...
}
```

So whichever you prefer.