ScatterPlotMatrix

The ScatterPlotMatrix is a multivariate data display that is capable of
showing n-dimensional data within an n x n matrix.  Each non-diagonal
entry (i,j) of the matrix contains a two-dimensional plot (currently,
implemented just as a Pablo XYGraph) of all data for dimension i versus 
all data for dimension j.  Each diagonal entry (k,k) of the matrix 
contains univariate information about dimension k (currently, this is
implemented as a Box and Whisker plot -- which shows the minimum,
maximum, quartiles and mean of the data on that dimension).

Clicking the left mouse button with the cursor inside the matrix will
bring up a callback specific to the matrix entry selected.  As with
other functional units, the configuration process allows specification
of minimum and maximum values and labels.

The ScatterPlotMatrix is implemented to work with the Pablo Snapshot
Utility.

Because the ScatterPlotMatrix is an amalgam of other Pablo FUs and
widgets, relevant attributes are exactly those of the component widgets.

Functional Unit Inputs:  1-dimensional array within within which the n
	                 dimensions are embedded, point-by-point.

