add: filters setting for nsfw blurring of posts, filtering subs in feed (also per tag)

[plebeius-eth]

NSFW-tagged subs are not included in the feed at the moment, but the user should have the option to include them manually. Also single posts marked as nsfw are blurred by default, but the user should have the option to show them by default.

I think the setting should be called "filters" to include all kinds of filters

[plebeius-eth]

5a078e7

I called it like reddit calls it, "content options". Instead of their general "hide mature content" option, we use 4 more specific options for each "nsfw" tag. There is a difference between "nsfw" in the broadest sense and actual "nsfw" (adult or gore) on Seedit: a subplebbit tagged as adult or gore will always tag all its posts as nsfw (but not blur them, because it makes no sense to blur posts in a nsfw sub, just like old reddit does it), whereas a subplebbit tagged as "broader nsfw" (by which I mean, tags that may or may not be considered nsfw depending on the client) won't show the "nsfw" label in a post of theirs unless the post itself is tagged (comment.nsfw is true). However, even those "broader nsfw" subs will display the "are you over 18?" alert, which displays for any sub with any "broad nsfw" tag.

anyways, it's confusing, but I think it can work. It's as close as possible to how old reddit does it. But unlike them, we'll also show the filtering in the topbar (#459). We have to test the UX so see if it's enjoyable.