- changing an object's name after construction is not allowed. Checks are performed
  when adding objects to parents that no duplicate names are used, changing the name
  to a duplicate name after adding it is therefore allowed and voids internal
  consistency.

- check for race in _task_pause()/_stop() since the TASK_LOCK is not held by the
  calling thread and the STREAM_LOCK not by the task code. 

- only emit EOS in PLAYING. Make sure elements reemit the EOS message when going to
  PLAYING again.

- implement return values from events in addition to the gboolean.

- implement query ala events as opposed to the current return value of only a 
  guint64. I don't have a use case where this a problem yet, though.

- implement state change order on get<->loop-get<->loop elements. This probably 
  requires a backtracking algorithm.

- implement iterators for traversing elements upstream or dowstream.

- unlinking pads in the PAUSED state needs to make sure the stream thread is not
  executing code. Can this be done with a flush to unlock all downstream chain
  functions?

- implement seek in GstPipeline.

- make events use GstStructure like GstMessage instead of the current union.

- make the seek event return the time where the seek will happen so that GstPipeline
  can update the stream time.

- implement clock selection as explained in part-gstpipeline.txt