chose consistent background color for home screen and gl view (background_light)

res/layout/fragment_home.xml

@@ -2,6 +2,7 @@
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
+    android:background="@android:color/background_light"
     android:orientation="vertical"
     android:weightSum="1" >
 

src/de/tudarmstadt/informatik/hostage/ui2/activity/MainActivity.java

@@ -58,7 +58,7 @@ public class MainActivity extends Activity {
 		ThreatIndicatorGLRenderer.setThreatLevel(0);
 		// set background color
 		TypedArray arr = getTheme().obtainStyledAttributes(
-				new int[] { android.R.attr.colorBackground });
+				new int[] { android.R.color.background_light });
 		ThreatIndicatorGLRenderer.setBackgroundColor(arr.getColor(0, 0xFFFFFF));
 		arr.recycle();