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

src/com/android/launcher3/DragSource.java

@@ -30,6 +30,17 @@ public interface DragSource {
      */
     boolean supportsFlingToDelete();
 
+    /**
+     * @return whether items dragged from this source supports 'App Info'
+     */
+    boolean supportsAppInfoDropTarget();
+
+    /**
+     * @return whether items dragged from this source supports 'Delete' drop target (e.g. to remove
+     * a shortcut.
+     */
+    boolean supportsDeleteDropTarget();
+
     /*
      * @return the scale of the icons over the workspace icon size
      */