Moving drag-drop related code into a separate package.

This is per an earlier CR comment "we should probably move all this code to its own package (launcher3.dragndrop) in a separate cl".

I'm not moving DragSource because it's referred from gsa code.

Bug: 22609426
Change-Id: Ia7204dab99c0c395c66b77143a2d60411153f5f3
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index ffa98c5..62e0816 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -103,6 +103,9 @@
 import com.android.launcher3.compat.UserHandleCompat;
 import com.android.launcher3.compat.UserManagerCompat;
 import com.android.launcher3.config.ProviderConfig;
+import com.android.launcher3.dragndrop.DragController;
+import com.android.launcher3.dragndrop.DragLayer;
+import com.android.launcher3.dragndrop.DragView;
 import com.android.launcher3.model.WidgetsModel;
 import com.android.launcher3.util.ComponentKey;
 import com.android.launcher3.util.LongArrayMap;
@@ -131,7 +134,7 @@
 public class Launcher extends Activity
         implements View.OnClickListener, OnLongClickListener, LauncherModel.Callbacks,
                    View.OnTouchListener, PageSwitchListener, LauncherProviderChangeListener {
-    static final String TAG = "Launcher";
+    public static final String TAG = "Launcher";
     static final boolean LOGD = false;
 
     static final boolean PROFILE_STARTUP = false;