GUI: Sort headers in the Sampler result

**Marc Stern** ([Bug 66143](https://bz.apache.org/bugzilla//show_bug.cgi?id=66143&redirect=false)):
When using the GUI, we often have a lot of headers in the "Request headers" pane, and especially in the "Response header" one.
Having a "Sort/Raw" option (button/checkbox/dropdown) allowing to alphabetically sort them (or not obviously) would, in some situations, be a great time saver.
As this would be an option, it would stay backward-compatible.
I hope someone could find the time to implement this.
Thanks

OS: All