Add biginteger support.

Remove an empty file I commited by accident, and remove the duplicated
boolean type.
Add tests for parse failures in DateTypes.
Add tests for DateTimeType

Add some doc blocks too.
Rename traits to have Trait suffix.

By convention traits in CakePHP use the Trait suffix.
Add Interface suffix.

By convention Interfaces in CakePHP have Interface as a suffix.
Update AllDatabase Suite

Run all the tests for the new db api.
Rename another Trait.

Also make the PostgresDialectTrait extend SqlDialectTrait.