Validate all license-digger licenses are correctly detected

[pombredanne]

We should add as test files most of the files from KDE's license-digger originally by @cordlandwehr @kossebau and team.

• The repo is at https://invent.kde.org/sdk/licensedigger with a mirror at https://github.com/KDE/licensedigger/
• Attached is a subset of the repo with files we should test: license text, templates and test suites. This is a nice data set as there is a lot of manual curation work that went into to review all and every license headers in the many project of KDE. See licensedigger-master-cc4b24d3fb67afa8fb0a9ef61210588958eaf0f5.zip

I am fairly confident that we do detect all these, but we need to verify this, and we need highly accurate detection.

• Any license file text that is detected exactly by a matcher as a whole file or fragment should not be added as test, as this would be redundant.
• When a license text is detected approximately, this would be a candidate for rule addition.