v7 appcompat library

v7 appcompat library   
Part of [Android Jetpack](https://developer.android.com/jetpack).
Note:The appcompat library has migrated into the [AndroidX](https://developer.android.com/jetpack/androidx) library, which is an [Android Jetpack](https://developer.android.com/jetpack) component. See it in use in the [Sunflower](https://github.com/android/sunflower) demo app.