Registration form and other minor user interface enhancements.
- Improve registration form with tooltips & to allow correcting email address & make verification code more obvious
- Rename Library and Inbox to make the library contents more obvious
- Update Welcome Tour to reflect renaming of library & reword with other clarifications
- Enlarge default application font size for easier reading
- Prevent unnecessary saving of unmodified empty Assignment description
- Internal code updates for efficiency, maintainability, & reliability
- Update third-party dependencies for security, performance, & reliability