trim unneeded Lua functions

[naturallymitchell]

using https://github.com/kyren/rlua/commit/68b90e74b96bc013a73d75f6a2e1163a78b9f903

• [ ] io library
• [ ] math library
• [ ] pattern matching library
• [ ] print() (to use a lower level console output function, instead of Speakeasy's log library, the log crate bindings are there, see also https://github.com/foundpatterns/torchbear/issues/116 )
• [ ] debug library (the unsafe parts) (done separately unless this new approach would work better) ...