refactoring based on findbugs guidelines

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

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

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

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

...ava/de/tlc4b/analysis/typerestriction/TypeRestrictor.java

src/main/java/de/tlc4b/btypes/StructType.java

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

src/main/java/de/tlc4b/tlc/TLCResults.java

src/test/java/de/tlc4b/coverage/IntegrationCoverageTest.java

src/test/java/de/tlc4b/tlc/integration/BugTest.java