GUI-176: Internationalization (i18n) framework

We have i18n message catalogs initialized for the following languages:

- English (en)
- Spanish (es)
- French (fr)
- German (de)
- Russian (ru)

Adding another catalog is via `python setup.py init_catalog -l it` (example uses Italian language code).

And translations are extracted via `make translations` (see Makefile in repo root).