add value group to support whitespace and comma delimiter
Merge branch 'master' of https://github.com/sschauss/ptt

Conflicts:
	ass02/src/main/scala/de/unikoblenz/ptt/lord/ass02/Ast.scala
	ass02/src/main/scala/de/unikoblenz/ptt/lord/ass02/PrettyPrinter.scala
remove double % symbol for hslx colours in pretty printer