[Internationalization] Replaced almost all Dutch text

Hello,

This is my first commit to Kate, or any KDE project in general.

I'm a native Dutch speaker, and have noticed that the kate-editor.org website had very bad Dutch translations. It appears that the translations were generated by an automatic translator, and the text was very bad IMO.

This MR changes a lot Dutch translation entries with correct Dutch.

LMK if I forgot some things :)

Tristan Gerritsen