Rethink argument matching in multi_model_.

[Nelson-Gon]

Given several methods, multi_model_1 should be able to match arguments only for the method in question and not throw warnings.

Something like:

[multi_model_1(train,"dist","speed",method = c("glm","lm"),metric = "rmse",control = ctrl,new_data = test,family="poisson")

should not throw any warnings.

Similarly, perhaps have several metrics eg c("accuracy","rmse") and match these to the relevant model?