Add PluginInflateContainer

PluginInflateContainer extends AutoReinflateContainer, except that
it also uses the plugin interface to allow the view to be swapped
out with something else.

Define an interface or abstract class as follows that includes the
version and action.

public interface MyInterface {
    public static final String ACTION =
            "com.android.systemui.action.PLUGIN_MYINTERFACE";

    public static final int VERSION = 1;

    void myImportantInterface();
}

Then put in a PluginInflateContainer to use and specify the interface
or class that will be implemented as viewType.  The layout specified
will be used by default and whenever a plugin is not present.

<com.android.systemui.PluginInflateContainer
    android:id="@+id/some_id"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout="@layout/my_default_component"
    systemui:viewType="com.android.systemui.plugins.MyInterface" />

Test: Manual
Change-Id: I2ef3fa8dbe344c4635df20056182c1c0b3846fdf