Update to Forge 10.12.1.1098. Fix GT startup crash. Fixes #1093

* Applied latest 1.6 fixes
* Applied missing TileEntityHopper optimizations from Spigot
* Fixed PluginClassLoader not handling net/minecraft/util packages.

CraftBukkit moves com,gnu,io,org packages used by vanilla to
net/minecraft/util. In order for plugins to work correctly, these packages
need to be located correctly by the PluginClassLoader. There are now
mappings that relocate each of these packages to the proper location on
our side. This will fix any issues with plugins failing to find classes
such as netty.