Added the mask Class: Useage: make a list of samples, call it from an external module with maskClass.Mask(waferSize, sampleList, maskLabel, fileName, toNeg=True). It will make a 5*5 inch square wafer with a circular center part of size waferSize (given in nm). if flag 'toNeg' is set to True, the mask will create an additional circle in layer two. This additional circle can be used to invert the mask conveniently in kLayout by performing an XOR operation on layer0 and layer2, and removing the original layers afterwards. The class automatically adds mask and chip labels for each chip on the wafer. Furthermore, except for saving the file as a gds file, it is possible to store the chips, with their labels, using pickle, using the maskClass.storeAll function. This uses pickle to serialize all chip objects with their labels, and also adds the wafer (with a label 'wafer')