quizzes/git: Add 'git commit --amend' question
answerdb: Timestamp answers

This may provide insight into the learning process (e.g. after I
reviewed the Git index, everyone started doing better).
cli: Add --all for easy review of previously-answered questions
Add --tag option and Question.tags sets for filtering large quizzes
quizzes/git: Tag existing questions
cli: Add the --tags option to list tags on the stack
cli: Add the --questions option to list questions on the stack

This lets you see what a quiz will ask without actually taking the
quiz.  In the future, it may be useful for jumping to a specific
question.
quizzes: Use complete sentences with punctation for prompts

This makes multi-sentence prompts less awkward.
question: Add support for list-of-lines prompts

We use lists of lines for other question attributes (e.g. setup,
teardown, answer).  Be consistent with multi-line prompts.

The handling is in Question.format_prompt() for easy access by any
consumer.  The `newline` option will make it easy to support
non-terminal output formats (e.g. `newline='<br/>'` for HTML).
quizzes/git: Convert multi-line prompts to lists
question: Add support for list-of-lines help

We use lists of lines for other question attributes (e.g. setup,
teardown, answer, prompt).  Be consistent with multi-line help.
quizzes: Convert multi-line help to lists