User Story 1: As a user I should be able to read the default settings
from an XML config file

Implemented read functionality from xml configuration file to settings
class for outputtype, path, default algorithm, default level and levels.
User Story 1: As a user I should be able to read the default settings
from an XML config file

adding new files for exceptions of read xml configuration files.
Merge branch 'master' of https://github.com/pysudoku/sudoku.git