For performance reasons we may well want to hint to the Passage that we
have done editing it for now and that it is safe to cache certain values
to speed up future reads.
Config allows an application to separate the responsibilities of setting
itself up, and providing a user interface from the real work that it needs
to do.
The core responsibility of the passage package is to store and collate
information about the structure of the Bible - The most important classes are
Passage, PassageTally and Strongs.