Add custom File Finder

[monyarm]

Features:

Get Common::File, even if it's nested multiple archives deep, from path string Common::FileFinder::findFile("ABC.X/DEF.FSA/ASFA.QEF");

Weighed, virtual folders, allow multiple folders/archives to be added together as a weighed virtual folder, and are searched through in order, based on weight
Common::FileFinder::addVirtual("name", ["realfolder1", "realarchive", "real folder 2"]);

Allow registering Archive subclass, and have FileFinder use it based on file extension, or failing that, by trying all formats.
Common::FileFinder::registerArchive<ArchiveSubClass>("extension");

Allow registering formats and have FileFinder auto decode it based on file extension
Common::FileFinder::registerImage<ImageDecoderSubClass>("extension");
Common::FileFinder::registerAudio<AudioDecoderSubclass>("extension");