AndroidX compatability

[Huulivoide]

Starting from API level 28, the old support libraries wont be updated anymore and instead one is expected to use the new AndroidX packages. To ensure old binary deps don't break, a new tool Jetify is used to mange the old support library references in them to the new scheme.

Sadly this does not work on RecyclerViewPager.

Problem:
android.support.v7.widget.ViewHolderDelegate gets transformed into androidx.appcompat.widget.ViewHolderDelegate, which is a wrong package. RecyclerView stuff is now located in androidx.recyclerview.widget package.

Solution:

• Migrate to AndroidX "support" libraries.
• Rename android.support.v7.widget.ViewHolderDelegate to androidx.recyclerview.widget.ViewHolderDelegate

[darekxan]

#218