* Added isDeterministic() to IFunctionBuilder i-face
* A test for non-deterministic mutations
* In MutationsInterpreter::validate() ensure deterministic functions
* Adjusted nondeterministic mutation tests
* Moved around some code in MutationsInterpreter::validate()
* Dropped unnecessary check in findFirstNonDeterministicFuncName()
* Corrections to IFunction{Base,Builder} interface