Add Markdownlint configuration file and tidy up some Markdown files
Adds Markdownlint (https://github.com/DavidAnson/markdownlint) configuration for the first time. This helps folks be more consistent while using editors that support the configuration. The configuration is current from the gitlab
project and is used in other projects also.
While here, tidied up some Markdown files in the project including resolving Markdownlint violations and updating some links.
Edited by Evan Read