Some Stream Conversion Tools

- gr.stream_to_streams(item_size, nstreams)

 - gr.streams_to_stream(item_size, nstreams)

 - gr.streams_to_vector(item_size, nstreams)

 - gr.vector_to_streams(item_size, nstream)

 - gr.stream_to_vector(item_size, vector_size)

 - gr.vector_to_stream(item_size, vector_size)

 * gr.stream_to_streams takes a single stream in, and produces nstreams

   out.  It effectively commutates the input items across the output

   streams.  The output streams are running at the input rate/nstreams

 * gr.streams_to_stream is the inverse of gr.stream_to_streams.

 * gr.streams_to_vector takes N streams in and produces a single

   stream of vectors out.  vector_element[0] comes from stream[0],

   vector_element[1] comes from stream[1], ...

 * gr.vector_to_streams is the inverse  of gr.streams_to_vector.

 * gr.stream_to_vector "reshapes" the input stream from N single

   items into a single output stream of vectors, each of which has N

   items.

 * gr.vector_to_stream is the inverse of gr.stream_to_vector.