% Find number of dimensions and extent along each dimension of
% the signal arrays. 
% - If 0D sqw object, nd=0,  sz=zeros(1,0) (nb: []==zeros(0,0))
% - if 1D sqw object, nd=1,  sz=n1
% - If 2D sqw object, nd=2,  sz=[n1,n2]
% - If 3D sqw object, nd=3,  sz=[n1,n2,n3]   even if n3=1
% - If 4D sqw object, nd=4,  sz=[n1,n2,n3,n4]  even if n4=1
%
% The convention is that size(sz)=1 x ndim
%
%   >> [nd,sz]=dimensions(w)
%%   Overloaded methods:
%      sqw/dimensions
%      testsigvar/dimensions
%      sigvar/dimensions
%      IX_dataset_3d/dimensions
%      IX_dataset_2d/dimensions
%      IX_dataset_1d/dimensions
%      sqw/dimensions
%      sigvar/dimensions
%      d4d/dimensions
%      d3d/dimensions
%      d2d/dimensions
%      d1d/dimensions
%      d0d/dimensions
%