added command line option: -constantsSetup <<BPredicate>>

src/main/java/de/b2tla/B2TLA.java

src/main/java/de/b2tla/B2TLAGlobals.java

src/main/java/de/b2tla/B2TlaTranslator.java

src/main/java/de/b2tla/TLCRunner.java

src/main/java/de/b2tla/analysis/AssignedVariablesFinder.java

src/main/java/de/b2tla/analysis/MachineContext.java

src/main/java/de/b2tla/analysis/NotSupportedConstructs.java

src/main/java/de/b2tla/analysis/Typechecker.java

...main/java/de/b2tla/analysis/UnchangedVariablesFinder.java

src/main/java/de/b2tla/exceptions/NotSupportedException.java

src/main/java/de/b2tla/prettyprint/TLAPrinter.java

src/test/java/de/b2tla/prettyprint/SetTest.java

src/test/java/de/b2tla/prettyprint/SubstitutionsTest.java

src/test/java/de/b2tla/tlc/integration/BasicsTest.java

src/test/java/de/b2tla/tlc/integration/ErrorTest.java

src/test/java/de/b2tla/typechecking/TestTypechecker.java

src/test/resources/basics/SetsTest.mch

src/test/resources/laws/SetLaws.mch