Replace -1 arguments by float('nan')

As we have seen in !40 (merged) using x!=x to detect if a default argument is nanseems to be faster than checking if it is -1. So maybe it makes sense to replace all the -1. float default arguments scattered across the components to make them faster and more consistent. As this will touch a lot of code and I am not yet fully sure about any negative effects I will keep this for discussion here.