title: Changing format of the date in SAPUI5 in DatePicker
body: <p>I'm trying to get value of DatePicker like so:</p>
  
  <pre><code>var start_date = sap.ui.getCore().byId("start_date_add").getValue();
  </code></pre>
  
  <p>but I get date in format Jul 29, 2015, 
  I would like to parse it so it is like so:
  2015-08-29. 
  Constructor for my date picker:</p>
  
  <pre><code>            new sap.ui.commons.DatePicker({
                  id: "start_date_add",
                  value: {
                      type: new sap.ui.model.type.Date({
                          pattern: "yyyy-MM-dd",
                          strictParsing: true
                      })
                  }
              }),
  </code></pre>
  
  <p>any help is appreciated</p>