title: extjs Combobox typeahead / auto selection for single character
body: <p>I am using extjs combobox for a sex field. It have two value "M" and "F". I want to make it usable with keyboard:</p>
  
  <pre><code> {
       xtype: 'combo',
       typeAhead: true,
       queryMode: 'local',
       minChars: 1,
       triggerAction: 'all',
       store: [
            ['M', 'M'],
            ['F', 'F']
       ]
   }
  </code></pre>
  
  <p>This works if I type "F<kbd>tab</kbd>" (uppercase), but not "f<kbd>tab</kbd>" (lowercase). If I check the code to this, the typeahead works:</p>
  
  <pre><code> store: [
       ['M', 'Male'],
       ['F', 'Female']
   ]
  </code></pre>
  
  <p>Any ways to keep the value as "M" and have lowercase works?</p>