Merge remote-tracking branch 'origin/jpa' into certificate-service

# Conflicts:
#	core/src/main/java/cz/muni/fi/core/data/repository/ExerciseRepository.java
#	core/src/main/java/cz/muni/fi/core/data/repository/LectureRepository.java
#	core/src/test/java/cz/muni/fi/core/facade/LectureFacadeTest.java