Use recommended approach for logging.

This splits the logging logic into
```logging```, which becomes a client library, wrapping freedom.core().getLogger()
and
```logger```, a freedom module implementing the well known 'console' API, which
can be installed as a custom freedom logger, via
```javascript
freedom('manifest.json', {
  logger: 'logger.json'
}).then(...)
```

In doing so, we can remove the ```core.console``` permission from all other
workers, and the logs will include freedom system errors.


Addresses https://github.com/uProxy/uproxy/issues/503
Perhaps not in this repo but in uproxy-networking, yes, we do call `setConsoleFilter`. Actually, I think that's the only method we care about -- and I'd be fine moving it to `logging.ts`, if it makes things easier.