Add link to local copy of Libre Art License

The server at artlibre.org has an issue and therefore re-users do
not currently have a way getting the license text from a reliable
source.

This patch adds a link to
https://commons.wikimedia.org/wiki/Commons:Free_Art_License_1.3

Change-Id: I6c6d5197d6bd5e94b6370c6ae4a80e3846693c29
Merge "Add link to local copy of Libre Art License"