Generalize support for 'App Info', 'Uninstall' and 'Delete'

This allows other DragSource's to allow this behaviour, instead of it being
tied to specific source types.

Change-Id: I06b7c39b1b34a0ae141245bcc13b6a0873a4c0fd
diff --git a/src/com/android/launcher3/Folder.java b/src/com/android/launcher3/Folder.java
index 1d234ff..50e2000 100644
--- a/src/com/android/launcher3/Folder.java
+++ b/src/com/android/launcher3/Folder.java
@@ -801,6 +801,16 @@
         return true;
     }
 
+    @Override
+    public boolean supportsAppInfoDropTarget() {
+        return false;
+    }
+
+    @Override
+    public boolean supportsDeleteDropTarget() {
+        return true;
+    }
+
     public void onFlingToDelete(DragObject d, int x, int y, PointF vec) {
         // Do nothing
     }