Add search hyperlink to item keyword terms

Update to yonghaoy's commit and pull request for yonghaoy:keyword-169. This fix adds a hyperlink for a search to each keyword term, instead of a single hyperlink for all search terms.

The URL and search options for the keyword "KEYWORD NO SPACES" are:

```
http://datadryad.org/discover?query=&submit=Go
&fq=dc.subject:{KEYWORD+NO+SPACES}
&filtertype=*
&filter=
&rpp=20
&sort_by=score
&order=DESC
```