v3.1.2 with some performance optimization

• [New] chart of overview at admin panel
• [New] menu item for importing data from v2
• [New] option of max size of uploaded file
• [New] search for closet
• [Improved] optimize performance
• [Improved] allow to re-upload textures which were setted to private
• [Fixed] comparing with undefined
• [Fixed] cache-control header when return_200_when_notfound is on
• [Fixed] PrettyPageException at setup pages
• [Fixed] typos in language files
• [Fixed] cache control of json profile