Update Metadata model for metadata_history usage

Update data model for Metadata.py to support archived metadata. Updates will include:

• metadata_id(to eventually be used as foreign key, defaults to None)
• add reviewed boolean parameter(defaults to False)
• change reviewed_by to updated_by(null on creation)
• change reviewed_time to updated_time(null on creation)

The last two changes are not functionally different than previously existing labels, but provide better context for what they will be used for