Some gathered utilities

This repo is a collection of utilities that otherwise were being copied around all the time. Most remarkable utilities right now are:

BindingAdapter with some convenience subclasses for RecyclerView adapters that use DataBinding
PaginatedBindingAdapters that combines previous, and also gives RxJava2 pagination support

`adapters` is top level package (this should be the only include)

Other dependencies are `common` `rxutil-api` and `rxutil-rxjava2`