* Added opacity change instead of blur for background image
* Fixed integer overflow when refreshing grid list
* Added slider to control background image opacity
* Added show background image button
* Added UI code for checkbox and English and Spanish translations for new UI elements
* Removed background image caching
* Background image update on apply/save
* Only recompute image if opacity or game changes
* Fixed segfault when trying to change opacity after table refresh
* Placed background image settings under GUI in settings file