Modified Files:
src_test/java/unit/de/fhworms/ztt/ox/examrepository/ProblemTest.java
src/java/de/fhworms/ztt/ox/examrepository/Problem.java
added removeAnswers(Collection answers) that removes all
Answers from this Problem that are also contained in the
specified Collection, returns true if the Problem contained
the specified Answer
modified removeAnswer(Answer answer) returns true if the Problem
contained the specified Answer
