Minor simplification of code
Added validation for four fields of CrosswordKind
Refactored location of data structures
Cleaned up class hierarchy in tests
Added validator for Sudoku charset
Added more validators for Sudoku elements
Added useall validator for WordSearch puzzles
Refactored validator to include field name
Refactored similar boolean validation functions
Added validators for retrace and zigzag entries
Added four more validators for WordSearch
Added validator for dictionary element
Ensure answer value is not an empty string
Removed function that is no longer needed
Added basic bool validator for Block puzzles