title: NSPredicate case insensitive string search with CloudKit
body: <p>I'm trying to search a String field of a CloudKit object. The following line successfully compiles and runs without error.</p>
  
  <pre><code>NSPredicate(format: "Title BEGINSWITH %@", "Apple")
  </code></pre>
  
  <p>Yet, when I try add case insensitive search, it the app crashes.</p>
  
  <pre><code>NSPredicate(format: "Title BEGINSWITH[cdl] %@", "Apple")
  </code></pre>
  
  <p>With error:</p>
  
  <pre><code>*** Terminating app due to uncaught exception 'CKException', reason: 'Invalid predicate: Title BEGINSWITH[cdl] "Apple" (Error Domain=CKErrorDomain Code=12 "Invalid operator in &lt;Title BEGINSWITH[cdl] "Apple"&gt;: Unsupported operator: BEGINSWITH" UserInfo=0x7fb69d02e910 {ck_isComparisonError=true, NSLocalizedDescription=Invalid operator in &lt;Title BEGINSWITH[cdl] "Apple"&gt;: Unsupported operator: BEGINSWITH, NSUnderlyingError=0x7fb69d02e9e0 "Unsupported operator: BEGINSWITH"})'
  </code></pre>