% Find number of dimensions and extent along each dimension of
% the signal arrays.
%
%   >> [nd,sz]=data_dims(data)
%
% - If 0D sqw object, nd=[], sz=zeros(1,0)
% - if 1D sqw object, nd=1,  sz=n1
% - If 2D sqw object, nd=2,  sz=[n1,n2]
% - If 3D sqw object, nd=2,  sz=[n1,n2,n3]   even if n3=1
% - If 4D sqw object, nd=2,  sz=[n1,n2,n3,n4]  even if n4=1
%