[DOC]Notebooks - Maintainability, Formatting, Testing

[krajendrannv]

Report incorrect documentation

Describe the problems or issues found in the documentation

1. There are multiple versions with some variations of same mortgage ETL notebooks. Even though, these are for different environments, we need
   a. coherent strategy to reflect the same core code/functionality across all versions
   b. method to update/maintain/test in an automated way for every release

2. Scala and Zepplin notebooks have formatting issues that doesn't render on GitHub. Need to root cause the problem and fix them.