Find the shape (tuple) of data in a NMRPipe file from parameters.
1-tuple is returned for 1D data, 2-tuple for 2D and non-stream 3D/4D data, 3-tuple or 4-tuple for stream 3D/4D data.
The last dimension of the tuple is length of the data in the file, the actual length of the data matrix may be half of this if the data is complex.