* works with python3
* argparse used for argument handling
* script can be run from tools dir and from repo's top dir as well
* support for schema 2.0 added
* support for add-ons added
* creates single guideline for core + add-ons on same date
* added --file and --all options
* keep old script in file jsonToRst_schema_1.py
Task: 42762
Story: 2009028
Change-Id: I6deb70fa39e8a51fcff0372217bbfc46282d7237