Miscellaneous updates.

- Re-enable route logging and simplify error handling.
- Simplify bhajan method callbacks.
- Don't restrict bhajan methods to approved only.
- Search only approved bhajans by default but allow unapproved override.
- Add tests for error handlers and unapproved search.
- Add detail to script start output.
- Throw error if database credentials are not provided in production
  mode.
- Formatting.