Add systemd unit

We are still managing the creation of the socket in python. We want to
configure the path to the socket in python.
Moved to setuptools
First shot at a client for dlstats
Fix configuration files. More options. FHS compliance.
Fix layout for unit testing

While I do prefer the previous folder layout, unittest more or less
impose that everything lives under the root directory of the package
(not the distribution package, remember that pythonistas are annoying
nitpickers). I want to run tests on the new client/server interface
because I am new to this and I guess I will need pretty extensive tests.