Settings rearrange and filtering improvements

1. Rearranged General and Filtering tabs
   • Moved stuff in General that hides things into Filtering
   • Changed some categories in General, moved more stuff into "Interface" since those settings kinda affect the whole thing. Changed "Timeline" into "Post Look & Feel"
   • Moved some categories into sub-categories of "Post Look & Feel".
   • Overall where stuff is located should be saner.
2. Added missing "Hide muted threads" option (defaults to true)
3. Changed how filtering works:
   • hideFilteredStatuses hides EVERYTHING hideable - muted threads, wordfiltered, muted users.
   • hideMutedPosts aka "hideMutedUsers" - only hides posts by muted users
   • Quickfilter now only changes hideFilteredStatuses
4. Fixes stylistic issue where hidden statuses in notifications would still occupy 1px of height due to border

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