- Clean up Machines.pm POD
- Clean up Manifolds.pm POD

- Dynamic machines
- Allow Manifold and ByRecord to not use a merger if there is no handler
  set, so that you can use ByRecord( My::Filter, XML::SAX::Writer ) to
  write out multiple file instances.
- Get DocSplitter to be able to notify a 3rd party or run a closure when
  starting / stopping each split doc, to make renaming an output file easier

- Allow Manifold to be used to merge documents:
    Manifold( Parser, Parser, Parser )->parse;