Add --config parameter to command line interface

The config option is to allow passing values into the process.env of the
test environment when started.  The idea is to allow for some variance
inside of the environment that can be test-specific.  For example, code
may travel from dev to qa to prod, and it would be good to be able to
run the same tests in all 3 environments but all 3 environments have
their own servers to deal with.  It would be nice to make the server URI
variable and populate it via the command line.  Each environment would
get its own .bat/.sh file to initiate the tests with environment
specific values.  It follows the dir command line pattern that was
already there.