title: jqGrid allows only numbers when editing cell
body: <p>I want to prevent my user from typing letters inside a numeric field.
  I saw that there is an option of: <code>editrules:{number:true}</code>, but this option will let the user click any key the user wants and only when row saved it will alert for illegal input. This is not good option for me. I want to prevent from the start the typing of keys that are not numbers (for example in a regular input I can use jQuery's <code>.numeric()</code>).</p>
  
  <p>How can this be done?</p>