wikipedia: remove extraneous &amp; from URL
wikipedia: unicode fixes
Wikipedia: fix 'didyoumean'
Wikipedia: Avoid showing useless 'non-result'.

This stops results like

View (previous 20 |  next 20) (20 | 50 | 100 | 250 | 500) http://en.wikipedia.org/wiki/Special:Search
Merge pull request #137 from kytvi2p/wikipediafixes

Various fixes for the Wikipedia plugin