supporting swipable home screens on xlarge devices

- icons and widgets on home screens can be "dimmed"
- celllayout no longer renders a dimmed version of itself, but instead its children make dimmed versions of themselves
- celllayout no longer always takes up full size of workspace, in landscape mode 
neighboring screens (celllayouts) are visible
- on xlarge devices, in landscape mode side screens are "dimmed"
- moved holographic outline helper to its own file
- fixed bug where mini-screens were still able to scroll left/right

Change-Id: I9e85ab4147edfae1e7525c3d11d42be3fabf4f6d
diff --git a/proguard.flags b/proguard.flags
index aa75f4a..82411eb 100644
--- a/proguard.flags
+++ b/proguard.flags
@@ -9,8 +9,8 @@
 }
 
 -keep class com.android.launcher2.CellLayout {
-  public float getDimmedBitmapAlpha();
-  public void setDimmedBitmapAlpha(float);
+  public float getBackgroundAlpha();
+  public void setBackgroundAlpha(float);
 }
 
 -keep class com.android.launcher2.AllApps3D$Defines {