Add tests for locale setting (#1823) ...

* Add tests for locale setting

- Adds Faker::Language module for testing languages with real-ish data
- Refactors global constants into Language model (See Issue#1696)
- Add specs to test locale change works

* Clean up language files to remove long names

* Add DB check in FastGettext initializer

* Set Memory cache for temporary caching solution

* Fix bug in Plan Rule