Refactor FolderIcon to separate the preview effect into it's own class

-> Created com.android.launcher3.folder package to house most folder-related files
   (aside from the FolderInfo) which is more related to the model than the UI.

Change-Id: I767063e1e4c775c01a799a3bede30cd94ac48ade
diff --git a/src/com/android/launcher3/FolderInfo.java b/src/com/android/launcher3/FolderInfo.java
index 6e0dcd4..861a935 100644
--- a/src/com/android/launcher3/FolderInfo.java
+++ b/src/com/android/launcher3/FolderInfo.java
@@ -48,7 +48,7 @@
     /**
      * Whether this folder has been opened
      */
-    boolean opened;
+    public boolean opened;
 
     public int options;
 
@@ -105,7 +105,7 @@
 
     }
 
-    void addListener(FolderListener listener) {
+    public void addListener(FolderListener listener) {
         listeners.add(listener);
     }
 
@@ -127,7 +127,7 @@
         listeners.clear();
     }
 
-    interface FolderListener {
+    public interface FolderListener {
         public void onAdd(ShortcutInfo item);
         public void onRemove(ShortcutInfo item);
         public void onTitleChanged(CharSequence title);