CableLabs Signature and Mapping Spec tests

This submission contains the current set of Signature and Mapping Spec tests.

A small change was made to the python server to accommodate the current configuration of the Signature tests, but will be resolved soon. 
Can we change this to make it clear that these comply with the terms in https://github.com/dlna/web-platform-tests/blob/master/CONTRIBUTING.md (assuming that this is ok)