Add integrated i18n support

possibly closing #36 and many related issues

I was looking for a nice way to internationalize webogram so there could be editions of it in different languages not only english.

Unfortunately I also couldn't find a drop-in-ready library or similar so I wrote one from scratch with high integration in angular and webogram in mind and am quite pleased with the result:

It's now easy to use and makes adding new locales am matter of 20min. See the included guide https://github.com/acran/webogram/blob/i18n/app/js/locales/Readme.md

Also I rebased my work on your latest master, so this should be a fast forward