Auto short URL

It is released from the troublesome work of shortening the URL and putting it on the signboard!
It automatically converts it to fit on the signboard using goo.gl or bit.ly.

• Implementation of automatic shortened URL function
• Improved behavior
• Improved GUI behavior
• Implement blocking, reloading, deleting cache etc of images
• Implement debug log function
• Preparation for coremods
• Change of image management method
• Added link correction function of gyazo and imgur
• SignPicture was modified to display when you gazed away from the signboard.