pretty printer: avoid to print the ListTerminator at the end of a syntatic list
replaced *.out files with generated outputs
modified the pretty printer to sort the cells of a bag according to the their order in user-declared configuration
updated *.out files in 4_imp++/lesson_6
updated *.out files in imp++/lesson_7
sort multiplicity cells according to alphabetic order; refactor the code to use comparator in sorting
used natural order in sorting map elements; fixed bugs; updated *.out files
Updated simple-untyped.k in the tutorial