Migration to OpenJDK 11, solves #218 #217 #195 #210 #209

• Adapt pom.xml files of all modules.
• Migrate GitLab workers to OpenJDK 11.
• Fix unit tests (please note the adaptions to the Maven code coverage plugin "JaCoCo" in commit f155f626).
• Fix script collect_line_and_branch_coverage.py (broken regex on Windows CI worker)
• Fix #209 (closed) on Windows worker (i.e. install opencl on either graphics card or CPU)
• Fix mvn compile fails unless running mvn clean before (see comment for error message)