Add support for basic auth

[spiffzilla]

When Elasticsearch are behind a basic auth login the plugin wont work.
Have tried do use plugin with a ES behind an Nginx proxy.

[misiupajor]

Thanks for the input @spiffzilla and you are indeed correct that it will not work as intended when basic auth is available. There is fundamental functionalities for supporting basic auth within the plugin, so I consider this an easy fix. I'll implement during the day and revert back.

[spiffzilla]

Great, I assume it will be argument controlled behaviour of the http auth functionality
.

[misiupajor]

Yes I think that would be the best approach, but I will make the arguments optional. If they are defined then basic auth is assumed

[misiupajor]

This is taking a bit longer than expected, but it's in the works. I'll ping you when I've fixed this!