Add Process Tree Visualizations to Dashboards

## What?

A process tree visualization would allow for visualizing of sequential or otherwise connected events, showing the relationship between them as a graph. Example is attached.


## Why?

Customer uses sysmon data to collect process create and process access events. In Graylog I can create aggregations but visualizing this data in a graph format like a tree is very helpful. It makes the flow of events easier to follow.

## Your Environment

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