Initial work on Vision support in text conversations and Image Editing

This is a huge patch which does some major refactoring like:

- renaming "Image Generation" to "Image Creation" in most places,
  to better match its new command (`!bai image create`)

- relocating image creation command (`!bai image` -> `!bai image create`),
  so it wouldn't conflict with the new image editing command (`!bai image edit`)

- introducing a new image editing command (`!bai image edit`), which
  is meant to work only with the OpenAI provider, but doesn't fully work yet
  due to https://github.com/64bit/async-openai/issues/364, though a next patch will fix it

- adding support for reading images off of Matrix conversations and forwarding them to
  text conversations. Works for OpenAI, but not for Anthropic yet
  (requires custom patches) and not for OpenAI-Compat (no support for
  images there)

- relocating some utils around (base64, mime)

docs/development.md

@@ -93,7 +93,7 @@ For getting started most quickly (and locally), we recommend using [LocalAI](#lo
 
 **Ollama is most lightweight** (~2GB for the container image + ~1.6GB for the model), but supports only [💬 text-generation](./features.md#-text-generation).
 
-**LocalAI requires 4x more disk space** (~6GB for the container image + ~12GB for the models), but supports [💬 text-generation](./features.md#-text-generation), [🗣️ text-to-speech](./features.md#️-text-to-speech), [🦻 speech-to-text](./features.md#-speech-to-text) and [🖼️ image-generation](./features.md#️-image-generation).
+**LocalAI requires 4x more disk space** (~6GB for the container image + ~12GB for the models), but supports [💬 text-generation](./features.md#-text-generation), [🗣️ text-to-speech](./features.md#️-text-to-speech), [🦻 speech-to-text](./features.md#-speech-to-text) and [🖼️ image-generation](./features.md#️-image-creation).
 
 **OpenAI supports all of these capabilities** as well and does not require powerful hardware or lots of disk space. However, it requires signup and an API key.