Allow to add manufacturer specific data to advertisement data

Hi,

I created the possibility to add manufacturer specific data to the advertisement data on Linux.
I added a method with allows to set advertisement data using a dictionary with variable content.

Thereby one may advertise a service using a dictionary like this: 
```js
bleno.startAdvertisingWithDict({'name': 'Bleno', 'serviceUuids': [my_service_uuid], 'manufacturerSpecificData': new Buffer("DATA")});
```

This method can be extended for further advertisement fields, so I made it the default implementation on linux however added compatibility to the standard startAdvertisting method.

Furthermore I added the same method for OS X, however by now it ignores everything but name and serviceUuids and defaults to the standard method.