Setup emulations and emulation args validation

[brokensound77]

resolves #28

This sets up the emulate and emulation commands.

TODO

• implement cleanup functionality (may punt to next PR)

Details

High level flow of emulate Command class

• if no emulation command passed -> print available
• if unknown command -> print available
• if known emulation command, load command class:
  • validate args
  • if valid, run emulation execute method

This flow instantiates the subclass calling BaseEmulation immediately to validate args before continuing.

Test

[brokensound77]

We should eventually review consistency of prints vs logger, or stdout vs stderr (see screenshot)

[brokensound77]

Pycharm could just being funky with the emulated terminal. Looks good in regular terminal