Add tour to be used for first edit (other than GettingStarted).

There are variants based on whether VisualEditor is installed,
since it controls the text of the edit source links too.

Bug: 51483
GitHub: https://github.com/wikimedia/mediawiki-extensions-GuidedTour/pull/1

Co-Author: Steven Walling <steven.walling@gmail.com>
Co-Author: Matthew Flaschen <mflaschen@wikimedia.org>
Change-Id: I38ecddd5d8afcf59b7918378b94201d59b907c65