Refactoring: dispatch "core" package modules into structs and utils, as it does not have a lot of sense anymore.

tests/util/test_statistics.py

@@ -0,0 +1,11 @@
+from bonobo.util.statistics import WithStatistics
+
+
+class MyThingWithStats(WithStatistics):
+    def get_statistics(self, *args, **kwargs):
+        return (('foo', 42), ('bar', 69), )
+
+
+def test_with_statistics():
+    o = MyThingWithStats()
+    assert o.get_statistics_as_string() == 'foo=42 bar=69'