Gettext localization master

Merged my Gettext localization work with master.

Previous talk in #1417. When merged fixes #263, #262, #221.
What I'm planning to do after merge:
- momentjs localization
- 24 hour time format in API calls
- iso date format in API calls
- localized plan generator output

I tested switching and time/date formats but it would be great if someone tests some more.