previous pull request

• add support for working with classes in class history and/or not accessible from SymbolList. Classes with more than 1 entry in class history will show up in browsers as Class[index-into-class-history]. Class that are not in the class history of a class reachable from SymbolList will show up in browsers as Class{class-oop}. You can browse the methods in these classes and add/remove methods
• package comparison improved in the package version browser (bi-directional comparisons)
• fix Issue Add builtIns comment into welcome shell console #201: fix typo in welcome message
• fix Issue Add a --compressed option to the bu command #202: Add a --compressed option to the bu command ... actually the new default for the bu command is create compressed backups. a --uncompressed option produces an uncompressed backup. A .gz suffix is appended to the backup file name when compressed
• as part of Issue Add a --compressed option to the bu command #202 work, add bu valudate for verifying the readability of a backup file.