Add NLP Sentence Classifier

[AyanSinhaMahapatra]

Solves the Issue - https://github.com/nexB/scancode-toolkit/issues/2181

Use Cases -

• [x] Determining License Class (Text/Notice/Tag/Reference) of Generated Rule Texts Model Link
• [x] Separating False Positives from License Tags. Model Link

Steps -

• [x] Fine Tune BERT models on License Texts.
• [x] Train Models on Scancode Rules. (For Determining License Class)
• [x] Train Models on Scancode Rules. (Separating False Positives in License Tags)
• [x] Model Validation and Comparing HyperParameters.
• [x] Implement Offline/Online Backup. Docs
• [x] Add Conda Environment.
• [x] Upload Models to huggingface website for easy download/loading.
• [x] Add Model Cards as README.md files here and at the huggingface website. (Some links at the MODEL cards will work after merging this PR)
• [ ] Improving Accuracy by Reviewing Results.