Possibility of adding more classes

Right now connection setting information is available as or is requested to be provided as generic `Map>` and from other network manager wrappers I've seen this is the norm. It's flexible but it's difficult and introduces a lot of boilerplate code to be written when these fields are accessed. For example simple use cases like connecting to a wireless network may requires an extensive `Map` object to be initialized however many fields don't need to be initialized it requires little more than an ssid and password for the most basic of connections.

I'm writing classes that should make it easier for me to serialize, de-serialize these Map objects to make them more accessible, if it's of interest I can integrate these classes into `nm.dart` as an optional extra in case users want a more accessible api.