ember-intl implementation fixes

[chadian]

Partially fixes #1561.

• remove empty string translations
• setting a missing translation message to an empty string
• Adding the fallback locale

cc @HospitalRun/core-maintainers

[MatthewDorner]

Took a look at the RTL with Urdu language, looks good except I noticed something else: the font changes. It even sometimes changes in the middle of a translation item, and there's no HTML or anything in the translation string, I wonder what it is. And I don't see this in any other locale even other RTL ones.

Also noticed some additional issues that were also present before the switch to intl so I can make a new issue for those later.

[MatthewDorner]

And, checked and that font thing happened before the RTL changes, but it is somehow related to switching to ember-intl. We can just put it with the other things to check out later.

Everything else looks good, are you still working on anything?

[chadian]

That's really interesting actually. I can't explain the font change for urdu. The characters look like they could be the same, I'm not sure if the change is acceptable or not either. I agree, let's do this as a separate issue and I'm happy to also investigate. Nothing else for this PR from my end, thanks! 👍

[MatthewDorner]

The characters look to be identical, just different font so I doubt it's a big deal. Thanks for the quick fixes.

[MatthewDorner]

Actually one more thing occurs to me, in #1458 we set all those translation keys to undefined instead of removing them so people could more easily see in the file what keys need to be translated.

Would it be better to comment them out instead of removing them entirely?

[MatthewDorner]

Maybe that's not a good idea either since if people add keys, they'll just forget to add commented out keys in the other languages so they still won't stay synced up.