Data class with model validation

[eduardomourar]

Implement/use a data class library to improve how to serialize/deserialize data while communicating with CloudFormation, and, the same time, validate the model. A library like TypedJSON should be easy to adopt without increasing too much the bundled size.

[eduardomourar]

Another important aspect to consider is handling nested arrays/object. Python plugin implemented that in aws-cloudformation/cloudformation-cli-python-plugin#80.