Add support for matrix / parameterization

[theseion]

Many of the tests are duplicates with minor variations in the payload. Test for many rules could be condensed to two or three tests with many payloads instead.

• extend the tests schema with support for a list / matrix of payloads
• add support in go-ftw

[fzipi]

Yeah, I wanted some time ago to use the same concept as nuclei-templates, with golang templating.

So adding a templated test, with data: {{ payload }} and a way to have tests generated for each payload...