Multimodal Support (Llava 1.5) (#821)

* llava v1.5 integration

* Point llama.cpp to fork

* Add llava shared library target

* Fix type

* Update llama.cpp

* Add llava api

* Revert changes to llama and llama_cpp

* Update llava example

* Add types for new gpt-4-vision-preview api

* Fix typo

* Update llama.cpp

* Update llama_types to match OpenAI v1 API

* Update ChatCompletionFunction type

* Reorder request parameters

* More API type fixes

* Even More Type Updates

* Add parameter for custom chat_handler to Llama class

* Fix circular import

* Convert to absolute imports

* Fix

* Fix pydantic Jsontype bug

* Accept list of prompt tokens in create_completion

* Add llava1.5 chat handler

* Add Multimodal notebook

* Clean up examples

* Add server docs

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Co-authored-by: Andrei Betlen <abetlen@gmail.com>