Direct access to fields as if they are trivial properties

This patch provides access to view model fields from XAML. The fields will behave like properties from XAML point of view. Public fields are useful in many cases, for example when they are readonly.

Access to field of type Independent<> is automatically converted to access to Value property on Independent<>. It is now possible to expose public Independent<> fields (usually readonly) without wrapping them in trivial properties.