use new _store_value method when replace option is set

this method was recently extracted and is used to store the value at the
right place and to trigger notify_change
fix check attribute initialisation
forward check parameter to load_data
rewrote INI parser so that check is enabled directly on store

data are now stored in an intermediate data structure so they
can be written in the tree using the element order of the model
added some intermediate tests display
fixed section_map