(Nothing, just another RuntimeException to BugException.)
Added Configuration(Version incompatibleImprovements) constructor, deprecated the Configuration() constructor. This makes setIncompatibleImprovements(Version) calls needless in most cases. Also, with incompatibleImprovements 2.3.21, the default ObjectWrapper changes to the one returned by DefaultObjectWrapper.getInstance(cfg.getIncompatibleImprovements()), so DefaultObjectWrapper doesn't have to be instantiated "manually" with the Version argument anymore. Furthermore, with incompatibleImprovements 2.3.21 the default TemplateLoader changes to the NullTemplateLoader, that  I have also just added.