title: How to create an observable that produces a single value and never completes
body: <p>I am aware of <code>Observable.Never()</code> as a way to create a sequence that never completes, but is there an extension/clean process for creating an observable that produces a single value and then never completes? Do i go with <code>Observable.Create(...)</code>? <code>Observable.Concat(Observable.Return(onlyValue), Observable.Never&lt;T&gt;())</code>? Or is there something built in or more "RXy" than this?</p>