Determine new issues

In case of a project containing some issues, we should determine which issues are caused by a specific pull request.

Approach:
- Store log files as artifacts on build system
- Check if a pull request buid
- Get target branch from pull request system
- Determine last successful build of target branch at time source branch was branched or earlier
- Retrieve log files from build system
- Parse old log files
- Compare log issues from old logfiles with current issues
- Filter issues reported to pull request system to issues not already available in the old logs
- Add column to issues report to mark new issues