Update share/site/duckduckgo/params.tx

Fixed the safe-search option: 

From: Safe Search: 	kp = 1 for On; kp = 1 for Off.

To: Safe Search: 	kp = 1 for On; kp = -1 for Off.
Merge pull request #3 from zekiel/patch-2

Update share/site/duckduckgo/params.tx