ColBERT Upstream Updates

[danielfleischer]

• IndexUpdater class for adding/removing new documents from an existing index.
• class_factory wrapper for HF_ColBERT to initializing new types of HF models:
  • AutoModel
  • BERT
  • Deberta
  • Electra
  • Roberta
  • XLMRoberta
• Example in README.

[danielfleischer]

I can mention the new feature; support for HF models is in terms of classes compatibility, no new weights.