Add Maven plugin for mutation testing using PIT about indriya HOT 1 OPEN

Thanks for the suggestion/question.

While this module does not use code-coverage (it was never the RI of JSR 363) we did so in unit-ri: https://coveralls.io/github/unitsofmeasurement/unit-ri?branch=master
and with a slightly different tool chain (also upgraded to Circle-CI 2.0 Flows) Indriya uses: https://codecov.io/gh/unitsofmeasurement/indriya

The coverage of Indriya could be much better (at least the 60%+ of the old RI), but I am not sure, if PIT would help us improve it?
If you want to demonstrate it in uom-se, please do so. For the RI and other parts of JSR 385, we would have to ask you to join the JCP at least as Associate Member and offer you to become a contributor to JSR 385, here in this alternate implementation of JSR 363 we can do without.

from indriya.