CPA and Fax support

WIP - tagging @justinaiken and @crienzo as interested parties.

* [x] - `<receivefax/>`
* [x] - `<fax/>`
* [x] - `<document/>`
* [x] - `<metadata/>`
* [x] - `<finish/>`
* [x] - Document pages attribute should be a collection of ranges