added explorer topic hover series highlight

vipra-cmd/src/main/java/de/vipra/cmd/lda/Analyzer.java

vipra-ui/app/html/explorer.html

vipra-ui/app/js/app.js

vipra-ui/app/js/config.js

vipra-ui/app/js/controllers.js

vipra-ui/app/js/directives.js

vipra-ui/app/js/factories.js

vipra-ui/app/js/helpers.js

vipra-ui/app/less/app.less

vipra-util/src/main/java/de/vipra/util/model/TopicWord.java