Add AWS datapipeline module.

This module allows creation and activation of [AWS Datapipelines](https://aws.amazon.com/datapipeline/), as well as deletion of existing ones. Modification of successfully activated pipelines is not possible (this is an AWS restriction, not one of the module). The pipeline definition (which can be rather complex), is expected in a JSON document, which can be templated (see embedded example) and is validated during upload.