title: Allow blank spaces in ag-grid filter
body: <p>I'm facing a problem with ag grid filter. I'm seeing that is ignoring the white spaces.</p>
  
  <p>Where can i set to the grid to allow blank spaces in the filter?
  Do you know any trick?
  Which part of the grid i can set acceptEmptyValuesFilter or something like that?? </p>
  
  <pre><code>onTextChange() {
      this.gridOptions.api.setQuickFilter(mySearchTextBox);
    }
  </code></pre>