Add VuMark Generation API

[adamtheturtle]

https://developer.vuforia.com/library/vuforia-engine/web-api/vumark-generation-web-api/

• Add support in vws-web-tools to create vumark database
• Understand naming VuCloud vs VuMark - Vucloud is the old name
• Consider - do we need more than one vumark database for the parallel tests? (the tests only ever can add, not delete) EDIT: GOING WITH ONLY ONE
• Add admin/create_secrets_files.py support for vumark databases
• Create a vumark database(s) and add the secrets to GitHub as per docs/source/contributing.rst
• Ingest the Vumark secrets in conftest.py
• Add one test which hits the real Vumark and is not covered by the mock at all
• Use verify_mock_vuforia fixture on that one test
• Add comprehensive tests / make them pass for vumark in the mock, e.g. Add validator error handling to generate_vumark_instance #2942
• Support vumark in the library
• Update the tests in the mock to use the library
• Repeat for inactive vumark database
• Add documentation (README and docs/)
• Make sure we have no references to VuCloud
• Add CHANGELOG entry
• Add to the CLI