Refactor DynamoDBStateActor to Updated StateStore Interface

[VaughnVernon]

@kmruiz

The various read() methods are already refactored.

See Line 159 for // TODO: Write sources needed to write parameter final List<Source<?>> sources

[VaughnVernon]

This is to help in implementing Entry<E> appending for StateStore writes:

https://stackoverflow.com/questions/14077414/dynamodb-increment-a-key-value