resetting *.arff files

[bettylorang]

Currently, every time we run the code, we have to manually clear/delete/rename the existing *.arff file. Otherwise, the numeric data for the new images will be appended to the old dataset. According to Maanas, this is because our classes are compiled once when the script is run and the images are iteratively fed into the Java class files generated and the attributes for each image are appended to the .arff file for each iteration.