v2 libraries require AWS SDK v1.11 to run

Since https://github.com/aws/aws-xray-sdk-java/issues/43 this library has provided compatibility with v2 of the standard AWS SDK. However, there are still a large number of dependencies on the (old) v1.11 SDK which means that it's necessary to have *both* sets of libraries on the classpath for this to work correctly:

- potential naming conflicts / code errors arise because a lot of classes are identically named (although in a different package structure)

- increases the bulk of applications since we need to bundle jars for both v1.11 and v2 SDKs

- additional complications such as having e.g. two sets of connection pools (one maintained by each SDK) which can lead to obscure bugs

Ideally, it would be possible to run using exclusively the v2 SDK: this is potentially quite a big undertaking since it would require rewriting large parts of the `core` package to remove any dependencies or v1.11, or else creating a new `core-v2` project largely as a copy of `core` and rewriting the necessary parts.