Lists in comments not validated

Problem/Motivation

It's hard to catch mistakes when people list things in comments.

 * Available configuration keys:
 *   - callable: The name of the callable method.

Should be

 * Available configuration keys:
 * - callable: The name of the callable method.

Proposed resolution

Add a sniff to catch this.

Lists should comply with: https://www.drupal.org/node/1354#lists

Remaining tasks

User interface changes

API changes

Data model changes