Improve NativeSearchQueryBuilder by adding convenience methods and modifying existing ones.

[xhaggi]

The NativeSearchQueryBuilder is missing some convenience methods and it contains some methods that are not in line with the other withXXX methods.

[sothawo]

please note that the whole client-integration will get a major rewrite in the next time, as we need to integrate the new Elasticsearch client, and the existing NativeSearchQueryBuilder will have to be replaced with something new; see #1853

[xhaggi]

IMO the changes I made to the NativeSearchQueryBuilder are minor. I have just opened a PR.