Smartdict test: [TDD] Smartdicts should not share state.
Smartdict: Smartdicts should not share state.
Smartdict test: [TDD] Ensure getKey uses the default argument.
Smartdict: Ensure getKey uses the default argument.

This bug was found by running `pychecker` on the soure code.
Type, Type test: Unify error hierarchy.
Type test: Static methods are no more.
Type test: Move is_array tests in separate class.
Type test: [TDD] Move validation inside Table.
Type: Move validation inside Table.
Type test: Simplify code.
Type: Move is_array.
Type test: [TDD] Signal undefined type when validating.
Type: Signal undefined type when validating.
Type test: [TDD] Validate arguments of constructors.
Type: Validate arguments of constructors.
Errata: Sort entries.
Errata: Constructor arguments should be valid types.
Type test: Verify API of Table.
Symbol, Symbol Test: Rename SymbolTable to just Table.