Rewrite list_unreleased_changes as python format and add new features.
By default it will behave as the previous version of this command (the
shell script).
Few new feature have been added in these changes to allow us to more
easily handle outputs in scripts.
Features added:
- allow user to retrieve results in json format
- allow user to retrieve results in yaml format
- allow user to ignore project not yet released
The shell script entry-point (tools) is still there but it will call
the python command in a venv instead of directly implement features.
Also the python version allow us to more surround this tools with unit tests.
Change-Id: Iaf86ecb1589c40102acb621b23ea12d71ed453bb
4912f7d5d0