Will finally be called when the whole document is processed
Important note: Every processor in the chain has to call doFinal() in its own doFinal() method.
InputProcessors should call it before doing other stuff to keep the processing order. Remember the
input-chain is in principle processed in the reverse order since we "leech" the events through the chain.
So that means that we should do the same for the doFinal method, otherwise we may run into troubles.