Backup Solr index.

Create a new CloudCrowd action to snapshot the Solr index, tar/gzip it, and store it on S3.

This isn't quite ready to go into production, as I've been unable to find out if the solr backup command:
  * Returns immediately, and you then need to repeatedly request status to determine if it's done
  * Or whether it waits until the snapshot is completed to return the response.

On my system with a very small index, it returns immediately and then status says its completed.  We'll have to run some tests on a larger search index to determine which method we need to accommodate.

I'm not sure how production is setup to read the solr config.  I modified the file: /solr/conf/solrconfig.xml which is where the development sunspot is reading from. Production & Staging may be setup differently and their config's will have to be modified in order to turn enable ReplicationHandler.