use better ImageView properties

should reduce memory consumption

Closes #3671
// FREEBIE

res/layout/thumbnail_view.xml

@@ -6,6 +6,7 @@
             android:id="@+id/thumbnail_image"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
+            android:scaleType="fitCenter"
             android:adjustViewBounds="true"
             android:contentDescription="@string/conversation_item__mms_image_description"
             android:layout_margin="@dimen/media_bubble_border_width"