Setting structure
It is composed by 3 private attributes
‘path’ contains the path of the loaded settings file
‘sections’ is a vector containing Section structures inside the settings file
‘messages_table’ is a vector of strings representing all error generated by Settings
Settings::get method returns this structure.
It is composed by 2 public attributes
first ‘value’ is the value returned
second ‘error’ can contains the possible error occured
during the Setting::get method or an empty string in case everything
has gone well.
see Setting get method for an example
GLOBAL_SECTION is a constant that can
be used to retrieve all values that do not have a section
due to the fact that when loading the settings file
a section name is empty or some lines of key/value pairs
were found before the first valid section