implemented task-card #1
updated javadoc in class Problem
Modified Files:
src/java/de/fhworms/ztt/ox/examrepository/Problem.java
Added Files:
src/java/de/fhworms/ztt/ox/examrepository/ProblemCatalog.java
src_test/java/unit/de/fhworms/ztt/ox/examrepository/ProblemCatalogTest.java
