Add command-line argument support via racket

[tnelson]

Prototype command-line support for setting options. There are two flags supported at the moment: -o and -O (lower and uppercase).

The lowercase -o will set an initial option value, but will be OVERRIDDEN by file-level option statements. E.g., this at the command line (note the need to escape the backquote):
racket ring_of_lights.frg -o run_sterling \'off -o verbose 1

• will NOT run sterling (because the example doesn't give a value for that option)
• WILL give verbose 5 output (because the example gives a value of 5 for that option)

In contrast, the uppercase -O will set the initial option value and disallow it changing. E.g.,
racket ring_of_lights.frg -o run_sterling \'off -O verbose 1
will give verbose 1 output.

The run-tests.sh script has been modified to give-O run_sterling \'off, which means that it can now be used vs. the examples folder for additional testing, as the run commands in those example models will not open browser tabs.