title: Add more indicies to existing multi index container
body: <p>I am currently using Boost::multi_index_container and its working great. However I wanted to encapsulate the code and create a template class that looks like this</p>
  
  <pre><code>template&lt;class T&gt;
  class LookUp
  {
      boost::multi_index&lt;T, indexed_by&lt;___predefined indices___&gt; &gt; myTable;
  
      void Foo();
  }
  </code></pre>
  
  <p>Essentially there are predefined indices used in this wrapper, but for a specialised T, I also want to add additional indices. Is it possible to add additional indices to <code>myTable</code>? Maybe additional template arguments? But the number of additional indices are unknown.</p>