ms of a 2D Gaussian. For more info on how a
 Gaussian relates to an ellipse see gauss2ellipse.

 USAGE
  mask = maskEllipse( mRows, nCols, cRow, cCol, ra, rb, phi )
  mask = maskEllipse( mRows, nCols, mu, C, [rad] )

 INPUTS [version 1]
  mRows   - number of rows in mask
  nCols   - number of columns in mask
  cRow    - the row location of the center of the ellipse
  cCol    - the column location of the center of the ellipse
  ra      - semi-major axis length (in pixels) of the ellipse
  rb      - semi-mino