Update SemanticExtraSpecialProperties.php

* Update version number (flagged since this is more sane)
* Typos and tweaks
* Added more authors to the file documentation
* Added "and others" to extension's registry
* Moved Säsongsmat.nu to the file documentation section since this is not an author
Update CHANGELOG.md

* Added release dates
* Tweaks
Update CONTRIBUTING.md
Update CONTRIBUTING.md
Update README.md
Merge branch 'master' of ssh://wmfgerrit/mediawiki/extensions/SemanticExtraSpecialProperties