BIG update to translations, due to additions and changes. Unfortunately Launchpad
translations don't work with gettext fuzzy matches, so I'm afraid there's a lot
of rework for translators.
* Add a few new translatable strings
* Update the list of files to scan with additionas and deletions
* Update the template (pot) and country (po) files
* Fix the preferences window to be translated (LP:#1245806) (accidentally added earlier in gtk3 rev 1565, just noting here)
* Update tab close button icon to match lighter gnome-terminal one (accidentally added earlier in gtk3 rev 1565, just noting here)
