Missing translations

There are some phrases without translations to CZ and DE in `src/Shopsys/ShopBundle/Resources/translations/messages.*.po`.
Besides there are new datafixtures which are not translated to german yet.

### Expected result
Translated:
- `Administration`
- `Demo product images by`
- `Do not distribute without permission.`
- `Martin Chefmaster`
- `Powered by`

Also translated datafixtures?