Beta Hybrid Citybus 8.1.0

This update fixes a couple torque allocation issues which, for the bus, will mainly affect the race configuration. There will also be an update notice when the bus spawns reminding everybody that a new core/common mod will be required for the next update to function. I'm moving the Lua code for the hybrid system to its own mod that this mod, the ETK hybrid mod, and any future hybrid mods can all share without each mod needing to ship its own copy of the code.