Migrate Non-Core Modules Out
Migrate Non-Core Modules Out

- Delete all modules that have been moved into separate projects.
- rename rxjava-core to rxjava

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