@Option to select tests for PitestTask

[Vampire]

Since Gradle 4.6 you can add custom command-line flags for tasks using the @option annotation.
It would be nice if the PitestTask had such an option like --tests for the Test task, to easily select the tests to run to not have to always run all tests when you are working on something specific.

[szpak]

Last of support for List/SetProperty (explained in #139) makes the implemention of that harder (more "hacky").

[szpak]

I implemented it as:

gw pitets --targetTests com.example.tests.*

which overrides targetTests defined in the project configuration. Does it satisfy your needed?

[Vampire]

Well, I called it --tests to have it consistent with the default Gradle Test task, but --targetTests will probably also do, as long as it works as intended. :-)

[Vampire]

Hm, while thinking about it, for my use-case it would actually be more helpful to be able to (also) set targetClasses, can you do the same for that one please? :-)