GitLab

Do not cast data returned from indexed_dataset to int64, rely on caller to cast to appropriate type.

Added logic for initilialize_megatron to work with cpu only jobs. This is necessary for several evaluation and processing scripts in downstream repos.

preprocess_data:
- Adds ability to not split sentences. This is used for gpt2 datasets.

- Adds ability to create multiple datasets from different json keys,
this is current untested.

indexed_dataset:
- Add new "get" function to get a portion of an entry.