refactoring

src/main/java/de/tlc4b/Translator.java

src/main/java/de/tlc4b/analysis/Typechecker.java

src/main/java/de/tlc4b/prettyprint/TLAPrinter.java

src/main/java/de/tlc4b/util/Ast2String.java

src/test/java/de/tlc4b/prettyprint/SubstitutionsTest.java

src/test/java/de/tlc4b/typechecking/TestTypechecker.java

src/test/java/de/tlc4b/util/TestUtil.java

src/test/java/testing/CompoundScopeTest.java