fun <A, B> <ERROR CLASS><A>.foldToObservableValue(initial: B, folderFun: (A, B) -> B): ObservableValue<B>foldToObservableValue takes an rx.Observable stream and creates an ObservableValue out of it.
initial - The initial value of the returned observable.folderFun - The transformation function to be called on the observable value when a new element is emitted on
the stream.