configurable linking to surveyor and summon. refs #423 refs #412
Merge branch 'master' into t423-link-to-articlesplus
limit to catalog items in summon search; added unittest ; refs #423 refs #412
created explicit tags instead of general purpose explore tag: e.g. explore_author; refs #423 refs #412
added test for subdivided subject heading searches and Summon
Merge pull request #511 from edsu/t423-link-to-articlesplus

T423 link to articlesplus