Add topic classifier

[caufieldjh]

Given an input text (or a directory of them) and a topic, this queries an LLM as to whether the text matches the topic.

Example:

$ ontogpt classify-by-topic -i temp/30091466.txt -m lbl/llama-3 --model-provider openai --api-base "https://api.cborg.lbl.gov" "clinical observations of human patients, including the diagnostic and therapeutic procedures used during their clinical care."
temp/30091466.txt       False