Google Code-in

There are a few coding convention errors in the IDS extension. These should be fixed, and once they are, code-sniffing added to the repository's continuous-integration.

• Add a composer.json file with a test script that runs parallel-lint and phpcs (see the BoilerPlate extension for an example).
• Fix the style problems in the extension's files (and check locally that they pass). (You could also run against the master branch of the mediawiki/mediawiki-codesniffer, if you want to be very avant-garde and catch more errors.)
• Update IDS's entry in layout.yaml of the integration/config repository to include the composer-test template.

This requires two patches to be submitted via Gerrit.