Prevent query from automatically executing after adding a value from aggregation

## What?
In 3.2 it became a lot more difficult to build queries with the new “aggregation” feature since whenever adding a value to the query (“add to query”) it directly executes the query. I don’t have to click on search anymore like in 3.1.

## Why?
3.2 makes building queries using “OR” a lot more complicated since the other aggregated values immediately disappear after adding one to the query so in 3.2 I can no longer select two or more values, add them to the query and put an OR in between.

Possible solution would be to add a check box to automatically execute the query and don't automatically execute when unchecked.

https://community.graylog.org/t/3-2-prevent-query-from-automatically-executing-after-adding-a-value-from-aggregation/14176

## Your Environment
* Graylog Version: 3.2