AWS SDK for Java 2.0 compatibility

[mattsb42-aws]

Problem

The AWS SDK for Java 2.0 will involve a significant change in that library's API and namespaces. We need to determine the right approach to ensuring compatibility with both the 1.0 and 2.0 libraries without incurring too many issues with code duplication.`

[josecorella]

No plans to support AWS SDK Java 2.0 in the dynamo encryption client