Also run on Java 8

Upstream commit: https://github.com/SpigotMC/BungeeCord/commit/5e5038c83936db8711bd0570b8edeb250f68cf26
Added async PreLoginEvent to change online mode per connection.

Signed-off-by: xxyy <devnull@nowak-at.net>
Adapt PreLoginEvent to protocol hack, Fixes #21