Add a "pwd" utility to userland.

It's implemented as a separate process. How cute is that.
Tasks now have a current working directory. Spawned tasks inherit their
parent task's working directory.
Currently everyone just uses "/" as there's no way to chdir().

VirtualFileSystem/InodeIdentifier.h

@@ -28,6 +28,11 @@ public:
         return m_fileSystemID == other.m_fileSystemID && m_index == other.m_index;
     }
 
+    bool operator!=(const InodeIdentifier& other) const
+    {
+        return m_fileSystemID != other.m_fileSystemID || m_index != other.m_index;
+    }
+
     InodeMetadata metadata() const;
     bool isRootInode() const;