Notification page overhaul

This adds basic notification grouping support. Right now this only includes favorites and boosts, but could theoretically be supported for follows as well.

There are a couple more improvements included:

• The margins and alignment for the interaction labels (the "X favorited your post" thing) are fixed, better and more.
  • The label is now bold on the notification page which helps visbility. It's normal everywhere else.
• Adds support for post updates (like when you subscribe to a specific person) in the filters, and also the desktop notifications. I don't really use this feature though, so I can't really test it that well.

Closes #45 (closed)