Allow index fetching to return a detailed result instead of a true/false value

This gives us the ability to see into why a replication might of failed and act on it if we need to. We use this enhancement for logging conditions so we can quantify what is happening with replication, get success rates, etc.

The idea is to create a public static class IndexFetchResult as an inner class to IndexFetcher that has strings that hold statuses that could occur while fetching an index.