Versionable unit tests & useDbConfig

* Versionable now supprts a global Configure set of defaults if set
* Versionable now supprts a new setting 'useDbConfig' (ignored when 'test')
* Versionable now has getDataBeforeSave() method (better than just saying look for a new property in the Model)
* VersionableBehaviorTest added with basics implemented
* minor comment and readme editing