Team management

[oguzkocer]

Implement team management as part of people management for blogs. Here are the initial screenshots for the feature: https://cloudup.com/cSrd17DVG6r

[roundhill]

👍

[oguzkocer]

Depending on if we'll implement people management for self-hosted users or not (afaik, we'll) we'll decide either we'll use the remote user id or a local db identifier (or possibly keep a reference to the blog and use a combination of remote id and the blog id) for the Person table. I am just making a note of it here and we can think about it when we resume this feature.

[oguzkocer]

Closed in #4100.