Stop indexing deleted content and provide a way to disable indexing on content delivery servers

[leethomascook]

… a batch that has 0 content id's which have not been deleted, so the indexer thinks it has finished processing.

We only found this becasue we had over 10k items trashed. I don't think people will want deleted content in the index anyway.

I also added a flag to allow you to disable indexing, if you have multiple servers. You don't want indexing to fire multiple times.