SeriesGuide API 2.1.0

• Migrate to AndroidX.
• Use Java 8 language features.

Android 11 support

When targeting Android 11 (SDK 30) add queries tags to allow the extension to see the SeriesGuide app (learn about package visiblity changes):

<manifest>
    <!-- When targeting SDK 30 (R), make the SeriesGuide app visible to this extension. -->
    <!-- https://developer.android.com/preview/privacy/package-visibility -->
    <queries>
        <package android:name="com.battlelancer.seriesguide" />
        <package android:name="com.uwetrottmann.seriesguide.amzn" />
    </queries>
</manifest>

See the README for details.