* PLT-914 Add mention notifications for replies on a comment thread
* remove useless store method
fix highlighting comments posted before th user write something to thread
* refactor out isCommentMention function after rebase
* change comment bar highlighting to replay icon mention highlighting
* settings and always visible highlight
* fix unit tests for new settings
* change highlight behaviour
- if any message in comment thread generates mention - all thread is highlighted
- remove always visible highlightion
* fix bug about the textarea in the center channel not clearing
* fix default settings value notify_props.comments
* do not highlight own comments if there is no other user's messages in thread
* refactor out ReactDOM.findDOMNode
* refactor out using of UserStore from component