Convert config file to be a singleton instance
The config.py currently uses some hacks to make sure that it does not get instanced twice. What we should actually be using is a metaclass constructor that looks like the one evilaliv3 wrote for GlobaLeaks.
This is the class: https://github.com/globaleaks/GLBackend/blob/c900929c8893ed5da47ea057845dfce486f25a26/globaleaks/utils/singleton.py
And this is how it's used: