Correct pluralization for hour and year in dutch

I just noticed that there is an error in the Dutch pluralization forms of `year` and `hour`.

It might sound wierd but in the Dutch language we don't use the plural form in time indications. So '2 years ago' should not be translated to '2 jaren geleden' but to '2 jaar geleden' (in English '2 year ago'). 

The same accounts for '2 hours ago', this should be translated to '2 uur geleden' (2 hour ago) and not '2 uren geleden'.

I tried to find an English source but could not find one. Here you have an advice (in Dutch) from 'het Genootschap Onze Taal' an organization specialized in the Dutch language: https://onzetaal.nl/taaladvies/advies/twintig-jaar-jaren

An other source for the hours is the Flemish Public Television: http://www.vrt.be/taal/uur-uren

A pull request reflecting the changes is attached.