META: improvement suggestions

[tanriol]

https://www.mozdev.org/bugs/show_bug.cgi?id=25372

• [ ] better skin support
• [ ] hide feeds with no unread items
• [ ] better support place
• [ ] scroll-to-top / collapse / star buttons on the bottom of an item

https://www.mozdev.org/bugs/show_bug.cgi?id=24529

• [ ] an easy way to mark everything as read

https://www.mozdev.org/bugs/show_bug.cgi?id=24527

• [ ] feed filtering

https://addons.mozilla.org/en-US/firefox/addon/digest/reviews/477508

• [ ] show feeds with unread items only in the feed list
• [ ] control sort order per-feed
• [ ] enhance "auto mark as read"
• [ ] naturalize shortcuts (ex. Space) and/or shortcut customization

https://forums.mozilla.org/addons/viewtopic.php?f=23&t=14582

• [ ] delete all items displayed/in-query ( https://forums.mozilla.org/addons/viewtopic.php?f=23&t=14582&p=29635#p29635 )