Kernel+ProcessManager: Add some more info to /proc/PID/fds

- "seekable": whether the fd is seekable or sequential.
- "class": which kernel C++ class implements this File.
- "offset": the current implicit POSIX API file offset.

Applications/ProcessManager/ProcessFileDescriptorMapModel.h

@@ -8,6 +8,9 @@ public:
     enum Column {
         FileDescriptor,
         Path,
+        Offset,
+        Access,
+        ClassName,
         __Count
     };