Major Description
Motive:
1. Scala is very flexible, if not having a code style guide in place, then it will easily be out of control.
2. There are a lot of doc errors which cannot be parsed by Scaladoc and JavaDoc. We should fix them.
Suggestions:
1. We can use Spark code style as major reference https://github.com/databricks/scala-style-guide, with a few modifications.
2. All doc errors should be fixed.
