Add some cases to test the link and base elements

Signed-off-by: xiaojunwu <xiaojunx.a.wu@intel.com>
Update tests for the base element a litte, and remove the link tests

- onerror checkpoint in link_events.html is covered by link-style-error-01.html
- link_type_mismatch_source.html uses setTimeout(); moreover, it won't fail
  even the feature is not implemented.
Add WIP tests for HTML's resolving URLs
Use add_cleanup
Test the ping attribute, plus some minor fixes
Update according to the new template

1. Update the code format
2. Update the reference specification
Test meta refresh
Test loading of nested browsing contests
Add spec link annotations
Test loading CSS with <link>
Test <script src>
Test loading images
Test loading video
Also test <source>
Test <track src>. (This test seems to expose a garbage collection bug in presto/blink/gecko.)
Test form submission
Test <base href>. Use blank.py instead of about:blank since the latter uses utf-8. Specify encoding in resource.py for types that would inherit.
Test microdata itemValue
Test Worker/SharedWorker constructors
Test EventSource constructor