Add an optional log line identifier to json output

[viktorbeck98]

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• [x] I have read and followed the contributing guide lines at https://github.com/ait-aecid/logdata-anomaly-miner/wiki/Git-development-workflow
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Fixes #1334

Submission specific

• [ ] This PR introduces breaking changes
• [ ] My change requires a change to the documentation
• [ ] I have updated the documentation accordingly
• [ ] I have added tests to cover my changes
• [ ] All new and existing tests passed

Describe changes:

• added a log line identifier in the json output
• introduced a parameter in the AMiner config to turn log line identifier on/off