Update all http links in XSD documentation to https

Description

There are a lot of links to the railML wiki in elements in the XSDs. These currently link to http://wiki.railml.org, and should be updated to link to https://wiki2.railml.org.

There are also some links to other web pages that can be updated from http to https.

Background

Links

• Forum discussion:
• Trac tickets:
• Wiki documentation:

Proposed solution

Replace all links to http://wiki.railml.org with https://wiki2.railml.org.

Check all other http links and update to https if available.