Rework server_add. It's smaller and leaner now, storing the list of

files out in a separate model for scalability.  Removed the "pause"
functionality.

- Server_Add_Controller extends Admin_Controller so that we don't have
  to check for admin every time.
- Task completion time now factors in the time it takes to walk the
  arbitrarily deep trees
- Moved checkbox management entirely into JS using jQuery
- Simplified the JS considerably

modules/server_add/module.info

@@ -1,3 +1,3 @@
 name = Server Add
 description = Allows authorized users to load images directly from your web server
-version = 1
+version = 2