Refactor getting_started.py example to demonstrate best-practices for defining command arguments

[tleonhardt]

The recommended way to define command arguments in cmd2 is to use either the @with_argparser or @with_annotated decorator.

The getting_startedlpy example is our best "Introduction to cmd2" example. As such, it should be fully displaying recommended best practices. We should refactor it to use both of these decorators in different commands.