Add blacklist and whitelist capabilities

[dshanske]

We need some way to better moderate things. Some things to be auto approved, some blocked...as simple as possible.

[pfefferle]

Isn't this a Webmention Feature?

[dshanske]

We have more data here, so we can enhance it

[dshanske]

The idea is that the webmention blacklist would have a filter enhanced by this.

[dshanske]

Closed as this is implemented in Webmentions and we will be eventually merging.