Repackage a bit differently

This MR proposes to re-package a bit to follow more closely https://www.python.org/dev/peps/pep-0517/ Mostly what it does is to move from setup.py to setup.cfg as well as a couple of other changes:

• Use fts3-rest (the existing name) as package name, since the API are the same. It helps the migration. Alternatively, the name fts3 is available on pypi (https://pypi.org/project/fts3/) so you could align the module import name and the package name
• The version number is managed by setuptools_scm instead of being handled manually, so it is aligned with gitlab tags
• Replace the scripts with proper console entrypoints, at the cost of moving src/cli to src/fts3/sripts and replacing - with _

The RPM build are failing because of moving these scripts. However, I am not quite sure that they are still useful, nor what they are supposed to ship exactly, so I'd rather let the massaging to you :-)

These MR was initiated by feedback from @cburr