Improve validation of the `info.license` field.
##Background
We're using the `info.license` field to indicate the license of content available through our APIs. At the moment, we only validate that the license field is present, but we don't actually check if the specified license is correct. Licenses for our content are generally well known, so it should be possible to introduce extra validation of the license field.
##Scope
[] Update the MediaWiki OpenAPI description generation process to use the license information defined within the project when setting the license. Use full-text/long-form license name in `info.license.name` and set `info.license.url`.
[] Introduce verification of `info.license` in manually created and external-module OADs. Validate it against a predefined list of well known licenses (determine the best way to store this list)
[] Introduce a linter rule to validate `info.license` against a list of predefined, accepted licenses.