[Conf] Simplify configuration file syntax

Created by: derkling

We currently use JSON as format for all the configuration file which is quite fragile when it comes to add/remove entries because of the dependency on proper placement of commas.

We should switch to a more robust syntax, possibilities are:

1. extend libs/utils/conf.py::JsonConf() to parse a comma-less file and properly add commas when needed just before parsing with the standard JSON loader
2. evaluate the usage of YAML as input format