View Results Tree : It should be possible to also test Headers content

**UbikLoadPack support** ([Bug 59977](https://bz.apache.org/bugzilla//show_bug.cgi?id=59977&redirect=false)):
Testers are great and highly increase productivity.
But they only allow testing Response data, while sometimes you need to extract data from headers with regex.

It would be nice to be able to test also that content.

Maybe an easy option is to make the text editable, so user would copy it and then apply his regex.

Ideally it would be nice to have a tab to select:
- request headers
- response headers
- response data

OS: All