BukkitFix door Pilzhut5

This addon fixes a few issues with BukkitDev (dev.bukkit.org) and the Bukkit Forums (bukkit.org).
Both sites have a few long-standing issues regarding accessibility, usability & design, which are addressed here. The following changes are applied to the sites:
BukkitDev (dev.bukkit.org):
- removed sidebar elements that made it impossible to reach some hitboxes
- fixed social icons on the login page
- fixed tooltip text color (#5d5d5d -> #fff)
- fixed download button tooltip "Download File2" -> "Download File"
- restored original BukkitDev logo
Forums (bukkit.org):
- restored BBCodes help page
- restored broken CSS (because it often breaks)