Basic support for languages

[chucker]

Best as I can tell, the current status is:

• [x] API: Support fetching a status's language
• [ ] API: Support writing it when posting a status
• [ ] API: Support for translation

Then there's the question of the GUI.

What Toot! does for writing statuses is multifold:

• it can set the language to whatever the keyboard layout is
• it can (my preference) detect the language based on what you've typed
• you can explicitly set the language

And then for reading them, I guess it detects if the language doesn't match your system language, and then offers to translate.

So, in terms of GUI, we want some of these:

• [ ] (Definitely) support for setting and/or detecting the language when writing a post (I'm not sure detection is trivial enough to be worth it)
• [ ] (Maybe) support for displaying the language for existing posts. I haven't seen this in most clients, I don't think.
• [ ] (Maybe) offering translation.