Add content controls for users

[darian-parrish]

Starting this as a discussion, not a proposal. This is a tough one but important to consider if DeSo is to be the future of social.

Inspired by this post by Sierra: https://diamondapp.com/posts/8ed23bcf166f5c32b6ca1706a999c4b9d50f5e143dca166ceea3a2539084b085

Possible changes:

• enable true deletion of posts
• enable selection of nodes that can show content
• better edit functionality