Add implementation stubs.
Implement AccountingEra.
Add initial comments.
Add serialization version.
Add enum for accounting year divisions enum.
Implement AccountingPeriod (...may need name change...)
Correct name of division enum in test.
Create AccountingChronology Builder stub.
Do initial base implementation of the chronology builder.
Add leap-week period to builder.
Switch tests to use builder for chronology.
Add missing parenthesis to method call...