Coverage per test

Using lcov to produce individual test coverages and iteratively summarize them in a subfolder to get a test coverage for the test-suite after all tests have been processed.

To apply individual test coverage add --individual-test-coverage in the command.

Right now, only the individual test coverages are printed to a file (filename: individual-test-coverages). Do we also need a file for the summarized test coverage for the whole test-suite? Right now this result is only printed to the console.