Move to configparser for user defined settings

[ntoll]

The ConfigParser class implements a well known config DSL with support built into core Python. Given the requirements for the integration test suite to configure local nodes on-the-fly, and the desire that simple user configuration should be possible (it currently isn't) then the following minimal requirement should be implemented:

• Specify and document the available settings that a user may specify.
• Specify and document the settings that can be overridden when in "test mode".

See https://docs.python.org/3.4/library/configparser.html for details.