Use html as the default output format

[psss]

Showing test, plan and story data in a human readable format will be the most frequent use case for the tmt web app. These links will be used in related Jira issues. Let's make them as short as possible. Example links:

• test: http://0.0.0.0:8000/?test-url=https://github.com/teemtee/tmt&test-name=/tests/pull/simple
• plan: http://0.0.0.0:8000/?plan-url=https://github.com/teemtee/tmt&plan-name=/plans/provision/virtual/the-rest
• both: http://0.0.0.0:8000/?test-url=https://github.com/teemtee/tmt&test-name=/tests/pull/simple&plan-url=https://github.com/teemtee/tmt&plan-name=/plans/provision/virtual/the-rest

The &format=html should not be needed.