Moved logic for retrieving chapters to statute class.
Tests for retrieving chapters are now done.
retrieveParts() basic functionality done and tested.
retrieveParts() is now tested for retrieving Part with number_index
Deleted unused variables.
Non-database variables have to be static for the software to work.
Renamed columns because names of variables have been changed in model classes.
Added mapping for parts and chapters in Statute.
mappedBy property had unsuitable value.
Variables had to be renamed.
Saving now works.