Updated, improved and fixed Dutch language strings (#2030)

* Fixed some words

* Improved and more consistent

* Fixes and a bit less 'je'

* Improved and more consistent

* Another round of improvements and consistency

* More improvements and less 'je'

* Update

* Updated with admin strings

* More improvements and additions - not complete yet, but most is there

* This is what we call in Dutch 'the English disease' :-)

* fix comma

* admin.reportsi

* not needed

* hopefully now fixed