Until version 1.5.1 the Nvidia Shield TV was listed in the Google Play Store as compatible with Minecraft. As of version 1.5.2 Minecraft is no longer compatible with the Nvidia Shield TV (or Android TV devices in general). So it can't be installed or updated anymore from the Play Store.

For adding Android TV support you just need to add the following properties to your AndroidManifest.xml

<manifest>
    <application android:banner="@drawable/banner" android:isGame="true">
        <activity>
            <intent-filter>
                <category android:name="android.intent.category.LEANBACK_LAUNCHER"/>
            </intent-filter>
        </activity>
    </application>
</manifest>

and place a banner graphic (320x180) in res/drawable named banner.png.