title: Unlist list of lists that have matrix elements to a list of matrices
body: <p>Suppose that A, B and C are matrices. And I have a list of them like this:</p>
  
  <pre><code>  list(A,list(B,C))
  </code></pre>
  
  <p>I want to convert it to this:</p>
  
  <pre><code>  list(A,B,C)
  </code></pre>
  
  <p>The <code>unlist</code> function convert the matrices to vectors!</p>
  
  <p>For example:</p>
  
  <pre><code>A=matrix(1:10,nrow=2)
  B=list(A,list(A,A))
  unlist(B)
  </code></pre>