Update frontend

Includes all changes from the cleanup branch

Description

Frontend now uses ChihuahUI and most pages (except statistics pages) are styled. To accomplish this, some other changes had to be made:

• Spotless frontend was added.
• A GNU AGPLv3 license header was added to all files.
• The old frontend has been renamed to archive.
• The project now effectively is just the old backend.
• Some weirdly named properties like GITLAB_SERVER_URL were moved to regular configuration properties.
• Liquibase was added.
• The existing authentication configuration has been replaced with regular LabraDoor authentication.
• All endpoints have been changed from camelCase to kebab-case.
• All templates have been changed from camelCase to snake_case.
• All packages have been changed from camelCase to lowercase.
• FancyPrint has been deprecated in favour of Logger.
• API controllers have been deprecated, as the relevant logic there should be moved to service methods.
• A simple error handler controller was added.
• Some dependencies were updated.
• Some non-working tests were disabled.
• A YAML file was added in favour of properties.