title: set first text on UISearchBar
body: <p>i want to set first text on my UISearchBar -the text is "Search"-, and the text will disappear when user start typing.
  just like this:</p>
  
  <p><img src="https://i.stack.imgur.com/fm1Mi.png" alt="alt text">
  <img src="https://i.stack.imgur.com/T1RK2.png" alt="alt text"></p>
  
  <p>how it could be.???
  thanx</p>