Negative test autogeneration framework

Generates and executes negative tests based on a json schema for the API.
It's using testscenarios lib to generate a test case for each variation.
It contains resource handling and result proofing of invalid requests.

Not covered in this patch (will be done later):
- Documentation
- Unit tests
- Actual json schemas for all APIs

Partially-implements: bp negative-tests
Co-author: David Kranz <dkranz@redhat.com>
Change-Id: I828f9b74c31f2e25c91e8149ecd7cd0b189ce99a
Merge "Negative test autogeneration framework"