Automatic iso loading

1. The program scans the files in the iso folder upon startup and adds them as the menu entries. No more parsing xml files
2. Every version of the same distro uses the same display picture and uses the same description
3. Display pictures in a separate folder. Distro description stored in a text file in a separate folder
4. The program no longer crashes when a matching picture or description is not found for an image. Instead, it uses a default picture and a description