Tests, Clean Up & Implementation of more features

Implemented/Fixed

 - Cash Flow Statement
 - Balance Sheet
 - Income Statement

Added

 - basic Owner's Equity Statement
 - more correctness checks for both reports and other operations
 - tests for various statements and important operations

API is now more consolidated (slugid classes now simply use "named" to get
an entry by it's slugid, sign retrieval is now standardized to avoid
confusion, etc).

Many fixes and tweaks ~

The database signature has been changed slightly; reset is required.