Update unit testing command line parser parameters:

* Add '--unittest-arg' command line argument
* Remove obsolete -unittest-format command line argument

Using '--unittest-arg' a string can be specified and be passed to the
unit_test runner. The string is provided to all suites that run, and
can be used by the Suites to customize their test behavior.
Add 'sample' npm test:
test/sample-test.js is the smallest possible npm test.