Oozie to Airflow 2.0.1

o2a package

• Update Oozie to Airflow documentation
• Update release Bash scripts

Oozie to Airflow 2.0.0

o2a package

• Update mappers and templates for control and action nodes for supporting Airflow>=2;
• Update requirements for supporting Airflow>=2;
• Add scripts for kokoro CI;
• Update documentation and tests;

o2a_lib package

• Update folder structure for o2a_libs;