Improvements to tests report usability

• highlight difference between groups and tests (different collapse icon)
• add test failure causes to the test name line
• add buttons to expand failed tests or all tests (no body)
• expand all failing tests on page open (no body) unless specific test is requested in the url, in which case only that test is expanded (with body)
• hide test results until the page is completely loaded

Closes #58 (closed) and #54 (closed)