HTML reporter: preserve query params when navigating to suites/tests

[boneskull]

PR #830 is woefully out-of-date, but we never fixed the issue, so this fixes the issue. To test:

1. Open browser test

$ open test/browser/index.html

2. Assert clicking on a suite drills-down to the suite
3. Assert clicking on a test drills-down to the test
4. Repeat step 1; ensure no querystring is present in URL
5. Append ?foo=bar to URL in browser
6. Repeat steps 2-3, asserting ?foo=bar remains in URL

[vsiao]

This can result in ?grep=foo&grep=bar&grep=baz if you keep clicking URLs in the HTML reporter. #830 ignores existing grep params, which is preferable.