INTEG-306: Wrong display activity after merging topic

Fix description:
* Update method updateActivityByTopic in ForumActivityUtils class to create new comment when comment associated to post doesn't exist.
* Use ForumActivityUtils.saveTopicActivity instead of ActivityManager.saveActivityNoReturn when merging topic.
INTEG-310: XSS vulnerability of Search Result Page

Fix description:
- Encode keyword during render process
INTEG-309: Code shown when commenting on Wiki activity

Fix description:
- Add load previous comment action
INTEG-250: [Unified Search] Hard-coded search settings

Fix description:
- Set search properties by using Portlet Preferences.
Merge commit 'd87db838365d468a1d77a1241910cc675e15cd33' into HEAD