delete obsolete files
move mixins/ files to top level
Split tests directory for infrastructure and widgets.
Widget tests are in widgetTests/ until widgets are moved to separate repository.
Move tests/infrastructure files to tests/.
Also removing DOH test references from module.js for tests that were converted to Intern.
Move tests/mixins files to tests/.
ownerDocumentBody is not longer defined,
use this.ownerDocument.body instead