Use @mixin for behaviors

PhpStorm since version 7.1 supports `@mixin` phpdoc tag. This feature added as checkbox.
Read more at http://blog.jetbrains.com/phpstorm/2013/11/phpstorm-7-1-eap-133-51/

Additional changes:
- Make `addModelMethodDoc` property sticky.
- Fixed few phpdocs in code.