Add support for other backend

[ParisNeo]

Expected Behavior

We should be able to select different backends. Need at least to support : 1- llamacpp 2- gpt-j 3- hugging face transformers models

Current Behavior

Only llamacpp is supported

[ParisNeo]

Now gpt-j backend is supported with a simplified mode (no word by word output)

[andzejsp]

this is completed