HV-878 Integrating Optional and JavaFX types

Ah yes, in your example (which uses the raw type of `Property`) the type parameter would indeed be resolved to `Object`. But we should support declarations such as the following:

    Property<String> stringProp = new SimpleStringProperty( "hello" );

Here, we can deduct `String` as the wrapped value type from the declaration and thus should allow to apply string constraints. I just had a quick look at the type hierarchy of JavaFX properties, and it seems as if we should actually have an unwrapper for `ObservableValue` which is the upmost type in the hierachy which wraps a value. WDYT?