Modernize lua read (part 2 & 3): C++ templating assurance (#7410)

* Modernize lua read (part 2 & 3): C++ templating assurance

Implement the boolean reader
Implement the string reader
Also remove unused & unimplemented script_error_handler
Add a reader with default value

src/script/lua_api/l_item.cpp

@@ -508,7 +508,7 @@ int ModApiItemMod::l_register_item_raw(lua_State *L)
 	std::string name;
 	lua_getfield(L, table, "name");
 	if(lua_isstring(L, -1)){
-		name = lua_tostring(L, -1);
+		name = readParam<std::string>(L, -1);
 		verbosestream<<"register_item_raw: "<<name<<std::endl;
 	} else {
 		throw LuaError("register_item_raw: name is not defined or not a string");