Terms of service and privacy policy feature.

If enabled, terms of service link will be shown in sign up page.

[Base for discussion on Loomio](https://www.loomio.org/d/ezlIV5rN/add-tos-and-pp-documents-for-podmins-to-use?proposal=k0LZg1M9#comment-128186).

So yeah, if enabled (default false), /terms route will work and contain either the basic template (default.haml) or custom written by podmin (terms.haml). Same templates are used for mobile too - we shouldn't duplicate these I think.

Also I'm sceptical whether there is need to allow somehow creating different language versions. Podmin can write it in whatever language they want or in different languages.

No tests yet, should probably write something for the setting <-> route functionality. Also is this as a feature something we want? Also the base template would need some discussion.

The terms are from [here](https://github.com/jaywink/terms-of-service) - though a little modified in this pull. I'm going to just delete that old repo. I've taken a print out from my local dev box for a little more convenient viewing :) [Check it out here](https://cloud.jasonrobinson.me/public.php?service=files&t=5e0e94be26f0a11b4a810d2bc72c5993).
That 'IANAL' text is a good idea. How about this slight rewording?

    -# NOTE! The default terms have not been checked over by a lawyer and
    -# thus are unlikely to provide full legal protection for all situations
    -# for a podmin using them. They are also not specific to all countries
    -# and jurisdictions. If you are unsure, please check with a lawyer.
    -# We provide these for podmins as some basic rules that podmins
    -# can communicate to users easily via the diaspora* server software.