CLI overhaul

[vivi]

Addresses #11.

• runs black formatter on main.py (should be another PR 🤫)
• uses questionary in lieu of flags (still supports flags as a legacy)
• introduces configuration files that are saved to disk and loaded in
• asks user if they want to autoload saved agent file (if exists)
• asks user if they want to regenerate embeddings
• no longer relies on readline

[cpacker]

Comments:

• Can we reorganize the personas in the selection list? Maybe put sam_pov first, then memgpt_starter, etc (basically sam_pov first, and memgpt_doc not first)
• At the user selection, should be "Which user" not "Which persona"
• Can we put a note that the user can create their own personas and users by adding text files inside the selection box?
• Can we put "Warning - you are running MemGPT with X" above "Running ..."? So two pink things are together

[cpacker]

Also should we sauce up the [exit by typing /exit] message? It's so sad and grey next to its multicolor friends.

[cpacker]

see comment