Starboard Mega-Issue

[andrewj-brown]

Making a mega-issue for all the things wrong with starboard.

• [ ] re-order DB interactions per PR #123
• [ ] add starboard msg-deletion handler per PR #123
• [ ] remove BlacklistedMessageException in favour of a StarboardMessagePair object per PR #123
• [ ] add static types to starboard per PR #123
• [ ] fix starboard post rendering when the user has left the server (top_role is not defined)
• [ ] add backup emoji for when/if :starhaj: is removed from the server (nitro moment)
• [ ] write comprehensive documentation & wiki-page for everything starboard does
• [ ] re-consider 'only one image/embed' policy now that discord condenses images