Also fix minor mistake in string "Files of type:".

Consistency checks (source -> translation):
* socket -> pistoke
* escape sequence -> ohjauskoodi
* (XML) tag -> tunniste
* XML declaration -> XML-esittely

Change-Id: Ia530f8bb0badea488afc7fb45dc62100b4f1dd96
Reviewed-by: Aki Koskinen <qt@akikoskinen.info>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

This is the first part and covers 4 files.
This contains translations by me, Aki Koskinen and
the following others from whom I have permission to commit this to Qt.

Originally-by: Jiri Grönroos <jiri.gronroos@iki.fi>
Originally-by: Jorma Karvonen <karvonen.jorma@gmail.com>
Originally-by: Kim Enkovaara <kim.enkovara@iki.fi>
Originally-by: Mikko Ikola <ikola@iki.fi>
Originally-by: Niklas Laxström <niklas.laxstrom+kdetrans@gmail.com>
Originally-by: Santtu Pajukanta <santtu@pajukanta.fi>
Originally-by: Teemu Rytilahti <tpr@iki.fi>
Originally-by: Tommi Nieminen <translator@legisign.org>

Change-Id: Icb1f79f3afec03e945a44df7aa464b1867eaa3c5
Reviewed-by: Aki Koskinen <qt@akikoskinen.info>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

Change-Id: I1ad47f33365b989d6f8229c6219cf61ba4b83b4a
Reviewed-by: Roman Paholík <wizzardsk@gmail.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>

Replace qt_de.ts by meta catalog.

Change-Id: Id6eed07f47084f9ef5cf156a99a41f884cf99d50
Reviewed-by: Robert Loehning <robert.loehning@digia.com>