Generic transport editor. (#1309)

Generic transport editor.

see #1301

* Fixed unit test.

* Added unit tests.

* Fixed unit test.

* Added transport module to test list.

* Moved relay transport backend to appropriate app.

see #1301

* Added missing file.

modoboa/urls.py

@@ -28,8 +28,8 @@ urlpatterns = [
     url('', include('modoboa.core.urls', namespace="core")),
     url('^user/forward/', forward, name="user_forward"),
     url('admin/', include('modoboa.admin.urls', namespace="admin")),
-    url('relaydomains/',
-        include('modoboa.relaydomains.urls', namespace="relaydomains")),
+    url(r'^transports/',
+        include("modoboa.transport.urls", namespace="transport")),
     # No namespace
     url(r'^accounts/password_reset/$', core_views.password_reset,
         name="password_reset"),