Negative values for subjectivity in Dutch sentiment analysis

[Aerylia]

The dutch sentiment file (see nl-sentiment.xml) has words with negative subjectivity, which does not respect the boundary values for subjectivity: [0.0, 1.0]. I did not check for how many cases, but the word "verloren" is an example.

Sentiment files for other languages may have negative subjectivity as well. Since this problem is similar to #125, but for Dutch in stead of French. This should be checked and fixed.