Inconsistent index size and document counts on index sets page

## Expected Behavior

The document and count and index size values on the index sets page should be consistent.

## Current Behavior

The total values for documents and index size at the top of the index sets page include all shards (replicas). The document count and index size values for each index set in the list don't include all shards but only the primary indices.

This can be confusing because adding up the documents count and index sizes doesn't result in the values that are shown in the total column at the top.


## Possible Solution

I think the first step is to be consistent with the values that are shown. Then we have to decide what information to show. With or without replicas, maybe even both. Both values can be important in some use cases.

## Steps to Reproduce (for bugs)

1. Navigate to "System / Indices"
2. Look at "Total" values and the values for each index set

## Context

The issue came up when researching how the index size for the size based index rotation strategy is calculated. The calculation in that rotation strategy is based on primary indices only. This might be another place where we might want to allow both values. (with and without replicas)

## Your Environment

* Graylog Version: 2.4.1