Do not error out when seed is calling without a positional argument.

Calling `odk.py seed` without any argument results in a crash because
the `repo` variable (supposed to hold the name of the repository) is set
to None, which is not expected by the Jinja template (it expects a
string).

When no positional arguments are specified, we set the `repo` variable
to `noname` instead, thereby allowing the creation of a full repository
with a dummy name instead of causing an error.

odk/odk.py

@@ -996,7 +996,7 @@ def seed(config, clean, outdir, templatedir, dependencies, title, user, source,
             raise Exception('max one repo; current={}'.format(repo))
         repo = repo[0]
     else:
-        repo = None
+        repo = "noname"
     mg.load_config(config,
                    imports=dependencies,
                    title=title,