Removing deprecated urls

Removing unused and deprecated urls

Re: https://bugzilla.mozilla.org/show_bug.cgi?id=1077705
this breaks all of the [manifest tests](https://github.com/mozilla/zamboni/blob/master/mkt/site/tests/test_views.py#L71-L121). you should probably either change the URL in the tests (and anywhere else `manifest.webapp` is called in Zamboni), rename `packaged.webapp` to `manifest.webapp`, or create another url pattern here for `views.package_manifest` but with `name='manifest.webapp'`.