WIKI-675: NPE but no warning message when 2 users edit the same page

Fix description: ix logic of logging users editing wiki page, add limit-living time for page edited without closing, add logic to remove log of these pages
WIKI-728: Empty Form of Attach File in Space wiki and User wiki pages
WIKI-765: User has not permission can see wiki page's content

Fix descriptuon: Return null when user has no read permission on required wiki page
WIKI-654: Display * character beside user fullname in warning message when editing a page

Fix description: Remove ** at the beginning and the end of user name in message
WIKI-523: When saving a draft, my typing is stopped
Fix description: Change ajax auto save request to asynch
WIKI-577 avoid creating new draft page after refreshing UIWikiPortlet