[#1368] Save any character in config file.

Problem description
===================

The configuration file has interoplation enabled so it has special meaning for % character.

We don't use interpolation and should remove that behavior.


Why we got into this (5 whys)
=============================

There were no tests for saving special character.


Changes description
===================

This first comments are some cleanup required to sync with some changes in server. There will be a separate branch for server to integrate these changes.

The last commit is the actual code for this branch.

I also had to fix some code after upgrading to python 2.7.


How to try and test the changes
===============================

reviewers @alibotean 

Check that tests are valid.