Added MappingFileSystemAdapter and adjusted some more stuff in the VFS module.

source/mijin/virtual_filesystem/stacked.hpp

@@ -28,7 +28,6 @@ class StackedFileSystemAdapter : public FileSystemAdapter
 private:
     std::vector<std::unique_ptr<FileSystemAdapter>> adapters_;
 public:
-    std::vector<fs::path> getRoots() override;
     fs::path getHomeFolder() override;
     std::vector<FileInfo> listFiles(const fs::path& folder) override;
     FileInfo getFileInfo(const fs::path& file) override;