Add graph_tool.clustering to graph_tool.all

src/graph_tool/all.py

@@ -37,6 +37,8 @@ from graph_tool.generation import *
 import graph_tool.generation
 from graph_tool.stats import *
 import graph_tool.stats
+from graph_tool.clustering import *
+import graph_tool.clustering
 from graph_tool.run_action import *
 graph_tool.run_action
 from graph_tool.util import *