add hyperlink for keyword to search by subject
Merge branch 'keyword-169' of github.com:yonghaoy/dryad-repo into yonghaoy-keyword-169
add link to each keyword term

Modified yonghaoy's commit to add a separate link to each keyword term,
per the feature request, instead of a single link spanning all terms.
updated xsl for changeset
make url for keyword link on data package page relative

updated stylesheet DryadItemSummary.xsl to make the keyword
term link relative to the current host, instead of the prod
server
Merge pull request #678 from rnathanday/yonghaoy-keyword-169

trello-169: add hyperlink for keyword to search by subject