Default error handler for functions

[3lyrion]

Like in sol2 with sol::protected_function::set_default_handler(...). This would get rid of silent failures when calling via LuaRef::operator() or LuaRef::call. It would also be nice to have a separate universal class for functions (without a signature). This would make it easier to store and use callbacks

[kunitoki]

I'm not a super fan of these globals (you can use callWithHandler) but i can add it if you find it useful.

You can still store LuaRef as universal class for callbacks and when you invoke it you will have to pass arguments and handle return values right ?

[3lyrion]

I want to call functions with an error handler in all cases, so I need a way to set a global one. Regarding universal functions, I mean a class with limited functionality compared to LuaRef