When we update the <title> after editing a topic, we should use the raw
`topic.title` as `topic.fancy_title` may contains some htmlentities and
will be displayed as is in the browser tab.
This fix the following issue:
> Incorrect HTML title after editing title/category of topic
> http://meta.discourse.org/t/incorrect-html-title-after-editing-title-category-of-topic/8136
added site_setting to control the default new_topic_duration_minutes
added 10 minutes option for auto_track_topics_after_msecs, default bumped up to 5 mins