Control the number of messages displayed in Views Messages Table

## Expected Behavior
The other Views widgets allow for the adjustment of the number of rows per field that are displayed. This is the expected behavior for the Messages widget as well .

## Current Behavior
The number of rows in the Messages widget is not an available setting.In a related note, there is no way to manage pagination.

## Possible Solution
Preferably by clicking on first field of the fields of the selected fields for the widget. Perhaps the Messages widget as a type could go away and it could just be a default variant of a table.

## Context
The View is a workflow, meant to drive the operator to a solution in as few clicks as possible. There are situations where more than 150 lines may need to be viewable, especially with availability of highlighting. This reduces the chance that the user will have to open another page to do a search from the Search page to discover how to limit the results in a manner such that they are all contained in the Messages widget. It also may not be desirable to limit the results at all. For instance, an IP Address conflict with DHCP servers may be interlaced with MANY other proper DHCP conversations. It may be desired to highlight the IP address and scan for other properties in the logs (perhaps VLAN sources for Bootp relay) without first limiting the search.

## Your Environment

* Graylog Version: 3.1.1
* Elasticsearch Version: 6.8.2
* MongoDB Version: 4.0.12
* Operating System: Linux
* Browser version: Chrome Version 77.0.3865.75 (Official Build) (64-bit)