added some loading messages

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

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

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

vipra-ui/app/html/entities/show.html

vipra-ui/app/html/explorer.html

vipra-ui/app/html/index.html

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

vipra-ui/app/html/topics/show.html

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

vipra-ui/app/html/words/show.html

vipra-ui/app/js/controllers.js

vipra-ui/app/less/app.less