Update hardcoded desktop filenames

https://bugzilla.gnome.org/show_bug.cgi?id=732247
Update gedit desktop file name
Improve releasing instructions

Instead of git-shortlog, use a git-log format that matches better with
what we need for NEWS.
Release version 3.13.4
trivial: Post release version bump
Drop the use of deprecated margin-left/right
Drop deprecated use of stock icons
Updated Lithuanian translation