[feature request] separate language packs from app

[945fc41467]

Wouldn’t be better to install language pack separately from the app ? I see two advantages :

• Unused languages take space on the hard disk. Even if it is not a lot, it is always too much when it is useless
• Unused languages take place in the selection button, and it would be far shorter to find the desired language in a list of 3-5 items than in the full list.

[shriramters]

That's a really good idea. The reason I didn't do this before was that I wanted the app to be completely offline ("no network access") but I agree that its wasteful to include all the models when you only use a few of them.

I will take some time to think about the logistics to provide each model separately for download.

PS: You should check out https://github.com/DavidVentura/firefox-translator/. this is a much more mature app that lets you download individual models and it also has the dictionary feature you mentioned in #47