Feature/docs api

This PR adds the documentation API as per:

* [ ] Added a DocumentationController
* [ ] Added DocumentationModel that consumes ZF\Configuration (also requires ZF\Configuration PR https://github.com/zfcampus/zf-configuration/pull/3)
* [ ] Tests for DocumentationModel
* [ ] Tests for DocumentationController
* [ ] Hal enable DocController

Other change (as per Matthews request):

* [ ] ensure input-filter is consistent throughout, use short non-reduntant names (ie: no rest_ or rpc_ prefixed child routes)