Update ASR scripts for tokenizer building and tarred dataset building
# Changelog
- Update docker container to nemo:1.0.1 
- Add Citrinet 1024 Gamma 0.25 model card for Mandarin to CTC char models
- Update tokenizer scripts to support adding bos, eos and pad tokens to SentencePiece tokenizers via `--spe_bos`, `--spe_eos` and `--spe_pad` flags.
- Update dataset building script to always provide a max length when building tarred datasets.

Signed-off-by: smajumdar <titu1994@gmail.com>