updated menus, added topic filter

...src/main/java/de/vipra/rest/resource/ArticleResource.java

vipra-ui/app/html/articles/index.html

vipra-ui/app/html/directives/article-menu.html

vipra-ui/app/html/directives/entity-menu.html

vipra-ui/app/html/directives/topic-chooser.html

vipra-ui/app/html/directives/topic-menu.html

vipra-ui/app/html/directives/word-menu.html

vipra-ui/app/js/controllers.js

vipra-ui/app/js/directives.js

vipra-ui/app/js/factories.js

vipra-ui/app/less/app.less