#1469 - Plain text versions of CC license files have disappeared from CC website

[reckart]

• Add common licenses like the CC licenses to the JAR and reference them locally
• Added an "optional" flag to allow marking artifacts which should not fail the materialization if they cannot be downloaded
• Updated dataset descriptions to refer to local license copies and update hashes if necessary (I had to fetch the license texts from the Wayback machine but they look legit)
• Fixed a few URLs which were no longer working
• Fixed the dataset description of the UPDT 1.3
• Text verification mode now also normalizes line endines

[reckart]

Jenkins, can you test this please?

[ukp-svc-jenkins]