Add an override to not track mutations for untested functions

[roookeee]

PITest will currently complain about surviving mutations for functions that are not tested at all. This prohibits to enforce a 100% mutation coverage without tediously excluding untested methods. This is useful as forcing a 100% mutation coverage combined with the outlined feature forces every test to be of the best quality instead of forcing the user to write unit tests for every method which is not the goal and/or usage area of pitest (at least how I see it).

I would need the given flag for the maven plugin at least.

[hcoles]

I think what you are looking for is #128 which I've been meaning to implement for some time now.

[roookeee]

As I read it its a bit different: I want every tested line to a have at least the given mutation coverage. Lines that are not covered at all by any test should not be included which is the case at the moment. I can only achieve 80% mutation coverage if I have only tested 80% of my application which is a bit misleading