Yaocho APIs

This adds a few APIs that were useful for Yaocho. These need to get to prod before I can put Yaocho in the marketplace.

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`self.kwargs` is like `**kwargs` in a normal view. It only comes from the url definitions, and so I don't think the user can hack URLs to change it. In particular, `kitsune/wiki/urls_api.py` line 10 defines what will end up in `self.kwargs`. The reason I include it here is because that's the way default version of this method works.