Fix "ignore_visility" behaviour in content/search, content/related_objects, content/related_objects_count, content/reverse_related_objects and content/reverse_related_objects_count :
Parameter's value should always be "false" by default (and not null)
Consequences : fix admin templates to force "ignore_visilibty=true" when necessary
Fix #EZP-19887
Remove useless linecode
Refs #EZP-19887
Remove useless linecode
Refs #EZP-19887
+ Move all default "ignore_visibility" variables to NULL
+ set ignore_visibility value to site.ini/SiteAccessSettings/ShowHiddenNodes if null in each fetching function
adding  	Adding BC notes for fetchRelatedObjectsCount changes