Security/Privacy overhaul

[danithaca]

The site now supports some general rules of security/privacy. But here we need to do a few things:

1. Document typical usage scenarios and expected results. For example, if users are friends to each other, then they are able look at each other's contact info. If users are friends of friends, then they can look at basic information. Etc.
2. Write automated test cases to make sure those are working.

In the future, we could allow users do privacy settings (like what FB does), but for now we don't.

[danithaca]

Some things we need to think about whether and when to show:

1. Children's name/age (change over time based on birthday)
2. People's street address
3. Other people's network
4. Other people's posts history
5. Profile description (might need to distinguish between public/private)