Scenario Builder script prompts are optional

There is now an 'interactive' option for the scenario builder script.

If you pass '-i' or '--interactive' then you will be prompted before any files are replaced, and the output will be more verbose. Otherwise the files will be silently created and moved into place.

From the help output of the script:

    usage: build_scenario.py [-h] [-i] [scenario]
    
    Compile scenario files.
    
    positional arguments:
      scenario           Scenario to build (ActiveShooter/Earthquake).
    
    optional arguments:
      -h, --help         show this help message and exit
      -i, --interactive  Prompt before replacing files.

This allows you to use the script like so:

    $ watch 'python build_scenario.py'

This will cause the files to be repeatedly recompiled every 2.0 seconds.