Support for unix file sockets

Additional support for unix file sockets. This is supported by nodes socket implementation by default. You have to give a file path instead of a port number.

To support URL scheme as port parameter as it is default in axon the common used unix:<filename> scheme is added to support file sockets without breaking stuff.

You can open a file socket by calling
```
    socket.bind("unix:/path/to/my/socket");
```
or
```
    socket.connect("unix:/path/to/my/socket");
```