[Doc] Updated translation files

[Peter Hofer]

Hi translators,

In order to fix the problem with wizard buttons (Back, Next, etc.) not being 
translated, translation files in the repository were updated to include these 
texts. Additionally, error messages for the package manager's terminal were 
added. Less than 10 phrases  in the .ts file were changed by this, other 
files have not been altered.

Please update your translations soon. Now that most other bugs are fixed, I 
hope we can release 1.0 at the beginning of next week.

Thanks for your appreciated work!

Peter