OpenCL backend / UX improvement / Speed improvement

New feature

• GPU OpenCL backend (to use GPU horsepower to upscale)
• support for more images and video file types

Improvements

• updated Python (3.7.9 -> 3.9.10)
• bugfix in AI model creation (speed boost ~10% with all models)
• deleted EDSR model (lighter .exe 110Mb -> 70Mb)
• general code cleanup

UX

• deleted EDSR model button
• new colors for left bar
• new button to select OpenCL backend
• removed AI models info under buttons
• removed NiceScaler icon
• added Github button
• drag&drop space cleaning