Added "offset feature" to equation_label_verify tool, which draws colored rectangles over expressions in the images. Offset is the page number to start on so that every page isn't redrawn each time updates are made to the GroundTruth.dat file. The GroundTruth.dat file holds the bounding boxes of all manually labeled expressions (labeled using the equation_labeler software).

Also labeled the expressions in one more image, data/16.png.