logilab-common #184774 Be able to produce JSON output from unittests [in-progress]

add a module that provides a couple of (pure unittest) TestRunner and a TestResult classes that produce JSON reports.

prioritynormal
typeenhancement
done in<not specified>
load1.000
load left1.000
closed by<not specified>
patch[jsonunittest] add a new jsonunittest module to make unittest produce JSON data (closes #184774) [reviewed]