Add Count All Message to "Message Count" Bar Chart of Default Stream View

## What?

Could you add the sum of all messages in "Message Count" Widget ?
Like this:

## Why?

This will be the same count as Single Number, but direct in Message Count display.
In Streams, It's always interesting to have directly the number of message of current search without add a new widget.

## Your Environment

* Graylog Version: 3.3.3
* Elasticsearch Version:
* MongoDB Version:
* Operating System:
* Browser version: