Improve rendering when creating, loading and resetting saved searches

A user is able to save a search, using the actions near the search bar. Creating, loading and resetting saved searches currently changes the URL (`history.push`) and forces all search page components to re-render.

We should refactor the current implementation to avoid the unnecessary renderings. For an example of the desired behaviour test the search reset for the default (not saved) search.

## Steps to Reproduce
1. Add a `console.log` to the `componentDidMount()` part of the Sidebar component
2. create, load or reset a saved search.

* Graylog Version: 3.2.0-beta.5-SNAPSHOT