Adds support for connecting to 1.7.10 modded servers using the FML|HS protocol:
https://wiki.vg/Minecraft_Forge_Handshake
* Handle client-bound plugin message packets
* Parse FML|HS plugin channel messages
* Add ModList serialization using Mod serializable, LenPrefixed<VarInt, Mod>
* Save forge_mods from server ping and send in FML|HS ModList packet
* Show Forge mod count in server ping listing
* Send acknowledgements, completing the handshake
* Add VarShort to custom payload len prefix replaces i16, fixes OOM on large modded servers
* Add custom CoFHLib's SendUUID packet -26
See explanation at https://github.com/SpigotMC/BungeeCord/issues/1437
This packet is defined by CoFHLib in https://github.com/CoFH/CoFHLib/blob/1.7.10/src/main/java/cofh/lib/util/helpers/SecurityHelper.java#L40
Fixes thread '' panicked at 'bad packet id 0xffffffe6 in Clientbound Play' with FTB:IE
327efcf043