Make breadcrumbs persist when you go up the chain.

[Torgen]

Fixes #260

[Torgen]

In this version there's a 'chat' button in the breadcrumbs for each level that has chat. It takes up a lot of space, it's weird when they all just say "chat", it takes up even more space if it says "Puzzle chat", "Round chat", etc., and it looks really weird with the icon but no label, both because rollover doesn't do anything when there's no text and because of all the empty space around it. I tried a version where I collapse the padding between the chat and the level it belongs to, but that looks weird when it's active because the padding is missing from only one side. I could try something like put "Puzzle: ${name} (spreadsheet icon) (link icon) (chat icon) Chat" in one <li> and underline the one that's currently in use.

[Torgen]

The "underline the selected view" behavior described in the previous message was implemented in 81891c5759c6ed3910fe2ae310d6ff2b0f23081b, but it also depends on the puzzle/round template unification from #300, so I'll send it as a separate PR once this and that are merged.