Use tokens instead of placeholders

The admin/quiz/settings/config page has a Notifications section that allows the administrator to configure emails that are sent to quiz-takers. Several "placeholders" are supported, such as !title, !sitename, etc.

These operate just like tokens from the Token module, which begs the question of why this particular wheel was re-invented. The Token module is widely used, extremely well supported, and familiar to site builders. Module maintainers can easily define custom tokens, and it provides dozens of other tokens right off the shelf.

Please consider integrating Quiz with Token and eliminating the placeholders.