v0.2.7 Release

Fixed a problem in the enum display name value converter. If the resource existed, but was empty, then not an empty string, but the name of the enum value was returned. Also added a custom boolean to visibility value converter, which, unlike the standard boolean to visibility converter, does not return DependencyProperty.UnsetValue, when the input value is null, but it returns Visibility.Collapsed. This is very helpful, when the binding is asynchronous, because in an asynchronous binding, the value can be undetermined (i.e. null) for a short period of time, which results in the control to be displayed for a short period of time, even if the binding value eventually evaluates to false.