Adding Exception handler to respond API Compliant XML
Adding rejection directives for Spray
Creating space for the TopicCreation directive
Initial work building the server

This is a broken commit with broken code however it's the start of piecing all
the other parts that will have to get built. Yes, it also does look like a
copy-paste job from ElasticMQ's SQSRestServerBuilder - that's the point, to keep
the codebase here looking close to that of ElasticMQ's own. Eventually in order
to support pushing messages into subscribed queues from topics we will have to
use a lot of ElasticMQ's code, it thus makes sense to keep them looking close.

I'll discuss any changes to syntax in ElasticMQ with its committers if
scalastyle finds anything undesirable in their code base.