contrib: Add a sample IPython shell with magic commands

[brenns10]

Here's the sample IPython shell code, edited down to be standalone. The docstring should contain everything you need to know, and here's a little demo:

Sadly, the "ERROR: root:Invalid alias" thing can't be avoided, unless you fully disable logging, which I didn't want to do. But as you can see, you get a pretty standard Ipython shell, with the ability to run custom commands as %command. And, if the command is not found in the globals, then you can actually run it as "command" without the prefix. And IPython always gives you a range of other magic commands, as well as shell command access with !.

The toy codebase I stripped it from actually had two CLIs:

1. The IPython one shown here
2. The standard drgn CLI, but with an added global: crash(). The crash() global swapped into a new CLI, which would allow you to execute the commands shown here, or swap back to the drgn CLI. I would have added all of the fun bash-isms and piping features of crash, but I ended up coming to the conclusion that reimplementing Crash on top of drgn didn't seem like a great use of my time.

That's why I didn't just write the commands as IPython magic class / magic functions. Also because I don't like the IPython magic API, but that's a separate story.

[brenns10]

Cleaning up: #367 is better than this, closing.