tahongshen add something:
1.add the message model
2.change the elements sidebar_*
3.achieve the MessagesController 'index' action
4.modify header.ctp
tahongshen add something:
1.modify db.sql, alter the table messages
2.modify Model file Comment.php, add the callback funtion aftersave()
3.modify MVC about messages, add the createMessages function.
4.modify webcontent controller file.
Merge branch 'master' of github.com:nwpu-graduation-project/MindParadise