Update editor main UI & controller

Make infinite scroll
Textarea autoresize
Add directive to attach element to scope
Scroll to active translation
Add translation descsription block

But hide it for now as the backend is not ready
Position sticky for translation header
UI tweak
Add save shortcut
Fix scroll directive
Red border for untranslated phrases
Green header
UI tweak
Search by text
Scroll delay
Add flags

Based on https://github.com/lipis/flag-icon-css
Make navbar a separate view
Merge html views into app.js