- Merges two strings from Likes and Mentions into the core YML.
- Adds commenting to core YML to indicate strings referenced by extensions.
- Changes `others_link` to `others_text` in Mentions.
- Removes obsolete `ref:` namespace from Mentions.
- Adds new sub-keys to replace key prefixes, and adjusts key names accordingly.
- Moves several button strings from `admin.permissions_` to `admin.permissions_controls`
- Merges `forum.settings_notify_` strings into `forum.settings`
- Rolls `forum.user_avatar_` strings into `forum.user`
- Moves the `user_deleted_text` to the `lib` namespace.
- Adds four other leftover strings to the `lib` namespace.
- Includes minor changes to formatting and comments.
Flarum is now powered by Symfony's Translation component, which has a more powerful pluralization system. The rules for all locales are included in core so they no longer need to be included per-language pack. See http://symfony.com/doc/current/components/translation/usage.html#pluralization to learn about the format.
closes#550
