Improvements:
- [ISSUE-505] Make "application/json" the default Content-Type in DataframeHandler #507
- CLI improvement - Add bento service as column for deployment list #514
- SageMaker deployment - error reading Azure user role info #510 by @HenryDashwood
- BentoML cli improvments #520, #519
- Add handler configs to BentoServiceMetadata proto and bentoml.yml file # 517
- Add support for list by labels #521