Bug 1055048: Move legal docs handling to separate app.

* Add generic view for legal docs.
* Convert privacy app to use new legal docs utils.
I know that this function is already in production and you're just moving it, but I had to learn the hard way that this sort of approach is very brittle and difficult to maintain. I'm not saying we can't use it in anger, but I think we should take a step back and consider other approaches before we promote this approach from a one-off solution to a general one. Perhaps instead of using BeautifulSoup to directly manipulate the html we could just use it to parse the data into a more fine-grained datastructure and keep all the html construction in the template?