Added TODOs to "VadereConfig".

    // Static Variables

    private static final Logger logger = Logger.getLogger(VadereConfig.class);

    // TODO: Define concept to read and write config file, i.e.:

    //  - Where is config file stored? "%AppData%" in Windows? "~/.config/" in GNU/Linux?

    //  - Write default config file if no config file exists.

    //  - Add flag "--config-file <path/to/file> to all(!) Vadere applications?

    // TODO: Provide following functionality:

    //  - Use OS-secific location: preferred home directory (or "%AppData%" in Windows or "~/.config" in Linux respectively).

    //  - Write default config file if no config file exists or errors occur while reading existing config file.

    //  - Add flag "--config-file <path/to/file> to all(!) Vadere applications.

    private static final String PATH_TO_CONFIG = "./vadere.conf";

    private static final VadereConfig SINGLETON_INSTANCE = new VadereConfig(PATH_TO_CONFIG);

    // Variables

    // TODO: Use "PropertiesConfiguration" and "dot" notation in "vadere.conf" and avoid "decorate()" method.

    //   See https://commons.apache.org/proper/commons-configuration/userguide_v1.10/howto_properties.html#Properties_files)

    private final INIConfiguration configuration;

    private final HashMap<String, IConfigSection> configSections;