Add documentation overview

Restore README.md (copy of doc/10_index.md)

Split documentation into multiple files

Add support for gpt-4-vision-preview model

Update README.md

Move the project to new location: aichatflow.dev/aibot

Remove duplicated paragraph from README.md

Remove duplicated paragraph from README.md

Fix inner links in README

Add documentation for custom functions

Comment out code that require newer version of go-openai package

Handle multi-part messages in OpenAI's endpoint

Fix bug related to prompt composition

Define gpt-4-vision-preview and gpt-4-1106-preview models

Change prompt composition procedure

This change prepares for supporting multi-part messages introduced by
OpenAI alongside the GPT-4 vision-preview model.

Migrate database schema to V2

Add support for multi-part message content to repare for new new OpenAI's API

- In new OpenAI's API user messages might conists of multi-part content.
  This pach allow for such message in templates and conversations.
- JSON message serialization was changed, which this renders the old database
  incompatible with new code.

Remove N parameter from DefaulRequest and Request messages

Add --stream-stages flag which enables streaming every model response

By default only last response is streamed. This option is useful with
multi-stage templates.

Add e2e tests for multi-stage templates