FORUM-578 | [Forum] No Poll inside Topic when clicking Last Post

Fix description:
- Problem: The value of property hasPoll on topic was cached on eXoCache, it doesn't update after adding the poll on topic.

- How to fix?: Always update value of property hasPoll on topic. Do not use eXoCache for this value.
FORUM-585 | Normal user having permission to post cannot post

Fix description:
Problem: Code error when checking permission in case of adding post. Before this fix, the value to check permission get from category is category.getCreateTopicRole(): That is wrong. Must be category.getPoster()

How to fix?: Correct to check permission when adding post. Replace category.getPoster() by category.getCreateTopicRole()
FORUM-559: [Answers] No result displayed if search with special chars

Fix description: use encodeSpecialCharInTitle method instead of encodeSpecialCharInSearchTerm to encode special character.