Re-write user interface

[hubertlepicki]

Curren user interface... kind of works. It's slow and ugly. I think it needs a rewrite.

What I was thinking about was a nice Angular.js and bootstrap based solution. I do not think we need a huge form with 2-way bindings, maybe we can live with a list of translations, and it only changes into editable form once you click on it.

There should be search and finding out relevant translations via filters as it is now.

The back-end can be extracted to form an API that can be used for in-line editing (see: #11)