title: can the order of the fragments in the backstack be changed programmatically
body: <p>Having A->B->c in back stack, A is at top.
  At the time it would like to have C to be on top, and keep A, B in the order in the stack. In the requirement it cannot have two C instances in the stack. The problem is if pop the C then all A, B is removed.</p>
  
  <p>What it wants is to have C->A->B now.</p>
  
  <p>Is it possible to achieve this with FragmentManager's api?</p>