Custom player name and SkinsRestorer integration

[Dantevg]

• [x] Add a separate server-name config item next to server-columns where you can use placeholders. This will replace the server's name in the first column (currently "Server").
• [x] Display the server's icon from the server list as the server's "player-head."
• [ ] For tables that only display the server's stats and not also player's stats, change the first column's name from "Player" to "Name" (I'm not sure about this one).
• [x] While at it, display the server's status as "online" or disable the status indicator, because it can never be afk or offline.
• [x] Integrate SkinsRestorer

[Dantevg]

Problem: lag spike with current SkinsRestorer integration (log attached: message.txt).

Possible solutions

• ✅ Done: Call net.skinsrestorer.api.SkinsRestorerAPI.getSkinData asynchronously
  • Still a problem, stats.json will just be very slow to load
• ✅ Done: Cache skins in WebStats
• Call net.skinsrestorer.shared.storage.SkinStorage.getSkinData with false as second argument?

  @param updateOutdated whether the skin data shall be looked up again if the timestamp is too far away

• Disable SkinsRestorer for valid online-mode players?