Add yaml serializer for addict dictionary

[jkrzemin]

Using kwargs to update root on kadet input right now can lead to quite a frustrating and a bit misleading error

yaml.representer.RepresenterError: ('cannot represent an object', {'name': 'http-api', 'port': 8080, 'targetPort': 8080, 'protocol': 'TCP'})

It's because a dictionary is of Dict type which is unknown to yaml serializer, which misleadingly (in context of this error message) has the same text representation as regular python dictionary.