This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
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