feat: System message template system to easily edit system messages.

[Maximilian-Winter]

Please describe the purpose of this pull request.
It adds a simple but effective template system for building the system message of memgpt.
It has predefined template fields that can be used to add parts of the default memgpt_chat system message.
The following shows the memgpt_chat system message in template form:

Each field adds a part of the system message of memgpt_chat, the template system will generate the memgpt system message automatically from it.

The template system get triggered when the system message string in the memgpt preset, ends with '_templated'. Like for example the following memgpt preset:

It then will load the built in template fields, like 'memgpt_introduction' or 'memgpt_realism_authenticity' and tries to load a file with the same name and path as the system message file, but having a file ending of '.yaml' consisting of field names with their respective content. The following is a complete example for instructing memgpt to talk like an old pirate:

memgpt_chat_pirate_templated.txt (in the user folder system_prompts)

memgpt_chat_pirate_templated.yaml (in the user folder system_prompts)

memgpt_pirate_preset.yaml (in the user folder presets)

Here are is the example in text form:

memgpt_chat_pirate_templated.txt (in the user folder system_prompts)

{memgpt_introduction}

{memgpt_realism_authenticity}

{memgpt_control_flow}

{memgpt_basic_functions}

{memgpt_memory_editing}

{memgpt_recall_memory}

{memgpt_core_memory}

{memgpt_archival_memory}

{memgpt_introduction_end}

{pirate_instruction}

memgpt_chat_pirate_templated.yaml (in the user folder system_prompts)

pirate_instruction: 'Always reponsond like an old pirate!!!'

memgpt_pirate_preset.yaml (in the user folder presets)

system_prompt: "memgpt_chat_pirate_templated"
functions:
  - "send_message"
  - "pause_heartbeats"
  - "core_memory_append"
  - "core_memory_replace"
  - "conversation_search"
  - "conversation_search_date"
  - "archival_memory_insert"
  - "archival_memory_search"

How to test
Start debug mode and look at the system message.

Have you tested this PR?
Yes.

Here is the resulting chat response of memgpt using the example preset:

Is your PR over 500 lines of code?
No. Very few lines!