Change to coremod, use transformers for mod-compatiblity

Switching to being a coremod allows all the current reflection code to be replaced by a combination of Access Transformers and custom class transforms to generate methods corresponding to the information provided by the API annotations.

Currently this branch works with the standard vanilla containers, with the exception of ContainerCreative for creative mode. The mods supported by InvTweaksModCompatibility and the API are not currently supported, but now that the base is there it shouldn't be too crazy adding in the support.