Migrate from deprecated Gtk.Stock

GTK+ 3.0 discouraged to use Gtk.Stock and is deprecated since GTK+ 3.10.

There is a guide to migrate to the recommended way to standard icon names and labels. Documents:

https://docs.google.com/document/d/1KCVPoYQBqMbDP11tHPpjW6uaEHrvLUmcDPqKAppCY8o/pub

https://docs.google.com/spreadsheet/pub?key=0AsPAM3pPwxagdGF4THNMMUpjUW5xMXZfdUNzMXhEa2c&output=html

Also, replace Gtk.Action with Glib.Action and Gtk.ActionGroup with Glib.ActionGroup.

[Uladox]

Already finished migrating from Gtk.Stock, Still working on Glib.Action

Thanks @Uladox, feel free to update file headers to add your author details for each file changed and update © year, also the AUTHORS file.