Finished ComputedQuestionObserver, added ActionListener
Fixed double quote display in labels
Implemented setValue() in CheckBox
Applied the visitor pattern to types to get rid of instance
Added typechecking to the demo
Added Unary expression class
Added save functionality
Changed Object to Void in Visitors
Merge branch 'master' of https://github.com/software-engineering-amsterdam/sea-of-ql
Merge branch 'master' of https://github.com/software-engineering-amsterdam/sea-of-ql