add product/__init__.py that includes declare_namespace() to support setuptools >= 3.0.

(cherry picked from commit 0db06a63)

.gitignore

@@ -8,4 +8,3 @@ erp5.util.egg-info/
 Products
 bt5/bt5list
 product/ERP5/bootstrap/bt5list
-product/__init__.py

product/__init__.py

+# See http://peak.telecommunity.com/DevCenter/setuptools#namespace-packages
+try:
+    __import__('pkg_resources').declare_namespace(__name__)
+except ImportError:
+    from pkgutil import extend_path
+    __path__ = extend_path(__path__, __name__)