- Configuration.LibationSettingsAreValid is true if Books property exists and is any non-null, non-empty string.
- If LibationSettingsAreValid is false, Libation will prompt user to set up Libation.
- When the main window is shown, Libation checks if the books directory exists, and if it doesn't, user is notified and prompted to change their setting
- When a user tries to liberate or convert a book, Books directory is validated and user notified if it does not exist.
