add cli parameter: --submodules
refactoring: now cli paramters are used only by the Settings class
remove trailing whitespaces
add  cli option: '--doctests'
refactor main(): if '--doctests' then run doctests
refactoring: 'main()', 'if __name__' and doctest invokation
add get_repo_name function
fix Settings usage
Settings: add submodules property
fix get_repo_name: now gets names with dots properly
backup_repos: fetch submodules if asked