title: Tinymce and removeformat option
body: <p>i'm using tinymce 4 and removeformat button. It works very well. 
  Now i need to remove only particular format (b, strong). I found</p>
  
  <pre><code>removeformat: [
                  {selector: 'b,strong,em,i,font,u,strike', remove : 'all', split : true, expand : false, block_expand: true, deep : true},
                  {selector: 'span', attributes : ['style', 'class'], remove : 'empty', split : true, expand : false, deep : true},                    
                  {selector: '*', attributes : ['style', 'class'], split : false, expand : false, deep : true}
              ],
  </code></pre>
  
  <p>Where is documentation about it? I need to understand every parameter (expand, deep...)</p>
  
  <p>If i select an image and click on remove format, i will lose classes. How can i avoid this behaviour? I tried to remove * selector line but it doesn't work.</p>
  
  <p>I tried also to attach original js to debug. I see my removeformat line is not considered. It considers only its default removeformat.</p>
  
  <p>Thanks</p>