title: How to allow only 2 decimal on a numberfield
body: <p>I would like to limit the number of decimals the user can write in the input.
  The field isn't shown in error when I write 850,9560 for exemple, here is my field :</p>
  
  <pre><code>{
      xtype: 'numberfield',
      fieldLabel: 'My field label',
      name: 'montant_sm',
      id: 'montant_sm_',
      decimalPrecision: 2,
      maxValue: 999.99,
      decimalSeparator: ','
  }
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/tf6o0.png" rel="nofollow noreferrer">My field without error for 880,9794 value</a></p>
  
  <p><a href="https://i.stack.imgur.com/gIg4H.png" rel="nofollow noreferrer">My field with max number exceeded displays correct error</a></p>
  
  <p>Do you know how 1 can set an error when the decimal is more than 2 with sencha ?
  Best regards.</p>