feat: Add MemGPT "Python Client"

[BabellDev]

Please describe the purpose of this pull request.
Implementation of local client to ease integration with other projects

How to test
Test code is TBD, but here is how a basic use might look:

from memgpt.config import AgentConfig
from memgpt.client.client import Client
from memgpt import constants

# Create an AgentConfig option from the inputs
agent_config = AgentConfig(
    name="BabellDev",
    persona=constants.DEFAULT_PERSONA,
    human=constants.DEFAULT_HUMAN,
    preset="memgpt_chat",
    model="gpt-4",
    model_endpoint_type="openai",
    model_endpoint="https://api.openai.com/v1",
    context_window=8192,
)

client = Client(auto_save=True)
agent_name = client.create_agent(agent_config=agent_config)


def send_message(message: str):
    response = client.user_message(agent_id=agent_name, message=message)
    for r in response:
        if "assistant_message" in r:
            print("ASSISTANT:", r["assistant_message"])


send_message("Hello my name is BabellDev, I enjoy open source development")

Have you tested this PR?
TDB

Related issues or PRs
#697

Is your PR over 500 lines of code?
No

Additional context
Add any other context or screenshots about the PR here.

[cpacker]

Made another pass an I think this should be good to go (unless there's anything else you see or notice that's wrong in the code I added @BabellDev)

As a final check, @BabellDev can you try both the examples in the README (also included a version for memgpt.readme.io, but it's identical so only need to test once)? Just to make sure that the documentation is correct for what's getting merged in.

Maybe try on a fresh / isolated install with no ~/.memgpt just to be safe.