Update the about dialog and have it show the core version and libtorrent version

deluge/core/core.py

@@ -801,3 +801,14 @@ class Core(component.Component):
 
         """
         return deluge.common.free_space(path)
+
+    @export
+    def get_libtorrent_version(self):
+        """
+        Returns the libtorrent version.
+
+        :returns: the version
+        :rtype: string
+
+        """
+        return lt.version