Translation via angular-translate

New version of translation mechanism via angular-translate.

What's new:
- more cleaner code for some translations
- language switch
- tables header translation
- translation of statuses and severity 
- usage of $translate service was excluded
- etc

TBD:
- translation in graphs ('translation' directive aren't working in <svg> area)
- translation of some text in JS code (another realisation is needed)
- localisation of date/time (switching of angularjs locales scripts)