Fixed gtk-doc error in GladeCreateWidgetFunc type definition.
GtkDialog: disabled use-header-bar property untill Glade supports GtkHeaderBar
GtkAboutDialog: ignore construct only use-header-bar property to force it to False in the runtime.
Bumped gtk dependancy to 3.12
Fixed bug in numeric property editors
Restored widgets classes that do not fail anymore in gtk 3.12
Rolling 3.18.1
Add dialog to advertise user survey
Added survey email strings, they will not be used directly in glade but
extracted and copied to https://people.gnome.org/~jpu/ to translate emails
sent to the user after the survey is completed.
Updated Polish translation
Updated Spanish translation
Update Spanish translation
Added missing \n in translation to fix build error
update zh_CN translation
Fixed typo in error messages
Added few comments for translators
Updated Czech translation
Updated Czech translation
Updated French translation
Updated Russian translation
Updated Russian translation
[l10n] Updated Italian translation.