Updated Italian translation
Updated Greek translation
Use set_accels_for_action().

https://bugzilla.gnome.org/show_bug.cgi?id=736298
Code fix as per the gnome coding conventions

Code cleanup as per gnome coding guidelines

https://bugzilla.gnome.org/show_bug.cgi?id=738924
Updated Czech translation
Change Finnish translation team web page to l10n.gnome.org
Correctly check XDG_CURRENT_DESKTOP environment variable.

The XDG_CURRENT_DESKTOP environment variable can contain a list of desktop names.
The existing code assumed it could only contain one name.

https://bugzilla.gnome.org/show_bug.cgi?id=739592
Updated Portuguese translation
Updated Norwegian bokmål translation.
Update build for appstream-util validate
Prepare 3.15.2
Updated Czech translation
Updated Spanish translation
Updated Turkish translation
Updated Hungarian translation