src/gtk-utils.c: non-void function should return a value

[bug #722002]
Updated Lithuanian translation
Updated Greek translation
updated for version 3.11.4
Updated Dutch translation master3.12
Finnish translation update
Updated Czech translation
ui: use "close" (not "Ok") buttons to close dialogs

https://bugzilla.gnome.org/show_bug.cgi?id=722051
Application: mark that we handle the command line

Otherwise activating the application a second time would fail.

https://bugzilla.gnome.org/show_bug.cgi?id=722492
l10n: Updated French translation