Move rx.util.functions to rx.functions
Move rx.util.functions to rx.functions

Eliminate dumping ground of rx.util

abersnaze/RxJavaString,ReactiveX/RxJavaString,ArekCzarnik/RxJavaString,Crystark/RxJavaString,davidmoten/RxJavaString,Crystark/RxJavaString,ReactiveX/RxJavaString