title: Add exception to min/max value in numberfield extjs 3
body: <p>a numberfield like this </p>
  
  <pre><code>xtype            : 'numberfield',  
  fieldLabel       : 'this is a label',
  id               : 'id',
  name             : 'id', 
  width            : 50,
  labelStyle       : 'width:300px',
  minValue         : 1,
  hideTrigger      : true,
  allowNegative    : false,
  maxValue         : 7,
  decimalPrecision : 1,
  allowPureDecimal : true,
  editable         : true,   
  allowBlank       : false
  </code></pre>
  
  <p>Accept numbers 1, 1.1, 3.5 ... 7</p>
  
  <p>But i need <strong>accept 0 too</strong>. Exists in extjs a property like exception or something that allows entering the 0 and also the minimum and maximum values that are established? </p>
  
  <p>I would appreciate it if someone could guide me</p>
  
  <p>Thanks for your time!</p>