AddDimension

  AddDimension adds a trailing singleton dimension to a variable in a
  MAT-file

  Example:
  AddDimension(FILENAME, VARNAME)

  FILENAME is a string with the name of the file (which should be a v6
  MAT-file).
  VARNAME is a string with the name of the target variable.
  NEWDATA is the matrix containing that data to add to VARNAME

  E.g. If VARNAME is a 100x100x3 matrix, AddDimension makes it a
  100x100x3x1 matrix (on disc - MATLAB's LOAD,  WHOS, SIZE etc will remove
  the singleton dimension). Subsequent calls to AppendMatrix will then add
  data to the fourth dimension creating.

  Restrictions: VARNAME must be the name of the final variable in FILENAME.
  VARNAME must be the name of a pre-existing variable. FileName must be a
  v6 MAT-file
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  This program is distributed without any warranty,
  without even the implied warranty of fitness for a particular purpose.
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  Author: Malcolm Lidierth 11/06
  Copyright © The Author & King's College London 2006
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