simplification
Merge branch 'master' of https://github.com/software-engineering-amsterdam/sea-of-ql
encapsulated visitors
Merge branch 'master' of https://github.com/software-engineering-amsterdam/sea-of-ql
merged evaluators
cleanup
Merge branch 'master' of https://github.com/software-engineering-amsterdam/sea-of-ql
prepared support for boolliteral in interpreter