[WIP] Release 3.0.3

Work in progress
@FinalAngel we'll revamp how this works. The meta_tags list will only contain values that the cms or re-usable apps actually deliberately set. We'll probably remove django-siteinfo completely. So also all [these metatags](https://github.com/divio/django-siteinfo/blob/master/siteinfo/context_processors.py#L16-30) would go away.