Adds angular-translate-loader-partial.
Adds language switcher widget.
Integrates json translations into zopf-courses.
Integrate the language switcher widget into the page.
Merge branch 'master' of github.com:mikl/zopf-stub-server

* 'master' of github.com:mikl/zopf-stub-server:
  Added log out link to the login widget.
  Made the basic login form work.