title: CKEditor add style on selection tag
body: <p>I'm trying to add inline style directly into a selection text tag e.g.
  I'm selecting<code>foo</code> within <code>&lt;a&gt;foo&lt;/a&gt;</code> and click on the bold button.
  Currently I have my config done so:</p>
  
  <pre><code>coreStyles_bold: {
    element: 'b',
    overrides: 'span',
    styles: { 'font-weight': 'bold' },
    childRule: function() {
      return false;
    }
  }
  </code></pre>
  
  <p>which will convert my <code>&lt;a&gt;foo&lt;/a&gt;</code> into </p>
  
  <pre><code>&lt;a&gt;&lt;span style="font-weight: bold;"&gt;foo&lt;/span&gt;&lt;/a&gt;
  </code></pre>
  
  <p>I would like to achieve:</p>
  
  <pre><code>&lt;a style="font-weight: bold;"&gt;foo&lt;/a&gt;
  </code></pre>
  
  <p>Is this possible in CKEditor?</p>