Corrected some errors

I used the german translation file as a model for the dutch translation.
Unfortunately, there were some errors in the german file ("Passwort:" should be "Password:")
I corrected both files, so things should be better now in both translations.
I also made some minor changes to the dutch translation, mostly capitalizing words. (it's hard to tell from the translation file if words should be capitalized or not) 
Sorry for all this trouble.