Redesign fs_dev, raw_dev, introducing device_partition and switch_fs.

In theory, one could mount an encrypted FAT partition itself coming from a disk image, etc.

fusee/fusee-secondary/src/switch_fs.h

@@ -0,0 +1,10 @@
+#ifndef FUSEE_SWITCH_FS_H
+#define FUSEE_SWITCH_FS_H
+
+#include "fs_dev.h"
+#include "raw_dev.h"
+
+int switchfs_mount_all(void);
+int switchfs_unmount_all(void);
+
+#endif