Update & improve the content from `.editorconfig`
Update & improve the content from `.editorconfig`

* Remove reference to `.travis.yml` as that file is not included.
* Add link to the site instead of explaining every line, and add
  comments only for when the information cannot be found on the site.
* Add `trim_trailing_whitespace` property.

sonarwhal/sonar,sonarwhal/sonar,alrra/sonar,sonarwhal/sonar,alrra/sonar,alrra/sonar