limit number of nodes to index at one time

Thanks for the great "dev" module.

I noticed with a large number of nodes (~ 133,000), re-indexing takes quite a while because the whole array of nodes has to be serialized and unserialized over and over again - see http://drupal.org/node/629794 for how this may be addressed in Drupal 7.

If you have a large site, it will help to set a limit and re-index in stages.

For example, the first 1500 nodes I indexed using this module took 33 minutes. I set a limit of 1500 (in line 82) and told it not to rebuild. That batch took only 10 minutes. I don't want to do this 90 times, so I'm going to hunt around for an optimal size for the batch.

The third batch of 15,000 took only 4 minutes to do the first 3,000, so clearly index time also depends on the node, but it may help if the batch API is not doing such hard work.

So if you ever decide to make this a full-featured module, a limit setting may help.