Show button for filter settings on filtered post

[nikclayton]

Is your feature request related to a problem? Please describe.

If a post has been filtered with "warn" there's a placeholder to show the post. This would be a good spot to include a button to edit that specific filter. The user might want to easily change the filter from warn to hide, for example.

Describe the solution you'd like

Either:

1. An additional UI control on the placeholder, sufficiently far from the control that shows the post. When tapped it opens the filter settings page for the filter that triggered the warn for this status.

Or:

2. An additional UI control on the placeholder, sufficiently far from the control that shows the post. When tapped it changes the filter that triggered the warn to a "hide" filter, and refreshes the display.

A complication with both of these approaches is that a single status might be matched by multiple filters. If that happens tapping the control should (maybe) open a menu listing the filters that matched, and allow the user to choose which one they want to change.

[nikclayton]

Implemented in #819