Upgrade storage for easier handling of model types

[jrriehl]

It would be better to add methods to allow easier storage and access of model types to avoid having to do things like this:

tables = {int(num): TableStatus(**status) for (num, status) in ctx.storage._data.items()}

[Archento]

I just stumbled across JsonPickle which may help with the storage problem. I was able to deserialise complex objects without issue and where json.dumps(obj.__dict__) was just not good enough.