Fix link so we don't redirect on first entry to questions.html
Keyboard shortcut to return test index -> dashboard
Tests should be indexed by unique ID, not array position so stale questions.html don't overwrite wrong entry if underlying data changes.
Fix dashboard previous test entry for nextId
Go back to last test question.
Add test timer.
Allow highlighting in review mode.
Fix percent grade
Restrict valid questions for tests to those with at least 3 discernible choices.
Clear prior timer timeout each time refreshTimer() is called.
Fix Mastery position
Present sequence questions in order in practice tests.
News message
Remove question/answer editor feature. Restore using the question-editor tag.
Refactor. 
* Move common code into util.js
* index.html, testindex.html, testgrade.html: use templating
* questions.html: separate features into separate classes
* Abstract storage functions to Storage class