Dutch updates to Mist interface

[actuallymentor]

Let me know if you want me to squash/reformat the commit tree.

What does it do?

Updates some Dutch translations and fixes minor typo/grammar errors I made in 2016.

Any helpful background information?

I did the original translation.

Which code should the reviewer start with?

N/a

New dependencies? What are they used for?

No.

Relevant screenshots?

N/a