Ability to add custom parameters from within allure.parameters

[OSnuszka]

I'm submitting a

• [ ] bug report
• [x] feature request
• [ ] support request => Please do not submit support request here, see note at the top of this template.

What is the current behavior?

Currently, custom parameters I am only able to add through @pytest.mark.parametrize("a,b,expected", ....) then I am able to get the following effect

What is the expected behavior?

I would like to be able to add custom parameters from within allure.parameters

Please tell us about your environment:

• Allure version: 2.1.0
• Test framework: pytest@3.0
• Allure adaptor: allure-pytest@2.0.0b1

[skhomuti]

looks like #565 should be raised up again

[OSnuszka]

It would be great be possible to merge these changes