SQS Extended Library Support

[jem-davies]

https://github.com/co-go/sqs-extended-client-go

Create functionality that will be able to handle this 'sqs-extended', where small messages <256KB, are put into the SQS queue as-is and big messages >256KB and <2GB are 'off loaded to s3' and a message contains a s3 bucket + s3 key reference.

Shouldn't be to bad because a lot of the functionality we need should already exist in the aws_s3 + aws_sqs inputs.