Create a check to make sure URLs remain backward compatible

[davsclaus]

When we re-organize content on the website we might accidentally shuffle the URLs around. We do check if within the website links are not broken, but we could also check if we changed any of the URLs so we know we broke links from other websites pointing to Camel and that we might need to add a redirect from old to the new content.
Perhaps looking up the current sitemap and the built sitemap on the pull request might be a way to check for any changes in the URL.

[davsclaus]

Moved from ASF JIRA to here: https://issues.apache.org/jira/browse/CAMEL-15970