Make Maps DBus activatable

https://bugzilla.gnome.org/show_bug.cgi?id=729361
Rename desktop file to GApplication application ID

This is needed in order to advertise that we support DBus activation.

https://bugzilla.gnome.org/show_bug.cgi?id=729361
Advertise DBus activatable status in desktop file

https://bugzilla.gnome.org/show_bug.cgi?id=729361