Fill actual and initial values of all existing preferences, as well as
create new preferences with initial == existing == default values, from
config file, that is stored in OS user preferences directory.
Loading of values from file does not happen in constructor!
First developer creates the instance, then adds prefs with default values,
only after that pref values can be populated from file by calling this method.
If file has a pref that is no defined by developer, new pref is created automatically.
Fill actual and initial values of all existing preferences, as well as create new preferences with initial == existing == default values, from config file, that is stored in OS user preferences directory.
Loading of values from file does not happen in constructor! First developer creates the instance, then adds prefs with default values, only after that pref values can be populated from file by calling this method. If file has a pref that is no defined by developer, new pref is created automatically.