Add a script and code template to generate a boiler plate file for a unit test.
Usage: scripts/create-unit-test.sh [-e] [-d] [-g GroupName] <libname> <TestDescription>

  Generates the boiler plate for a set of unit tests.  The output
  Positional arguments:
    <libname>  The base for the output file name, which will be of the
        form "<libname>_test.cpp".  Typically this would be the class
        name, or maybe a namespace holding free functions.

    <TestDescription> The brief description printed when the tests are
        run.  This is usually something like "MyClass tests". Quotes are
        required.

  Optional arguments:
    -e  Expert mode: Don't generate explanatory comments in the file.
    -d  Dry run:  echo the resulting file to stdout.
    -g  Set the test group name. This should be unique. If the option is
        not given, to_upper(<libname>) is used instead.