App keyboard

[amwatson]

This is a big of a hack: Some 3DS titles expect a system keyboard.

Normally in Citra android, an edittext is used to pull up the android keyboard to use as keyboard input. However, on Quest, a window management "bug" (in quotes because this behavior is probably undocumented) prevents the same technique from working (see note in vr_keyboard.xml)

I don't like that this completely fragments the codebase, and it might be a little buggy, but it does open CitraVR up to a number of important titles that rely on this behavior.

Some limitations:

• Keyboard may reject input based on an error, and that error isn't being
  visualized (it is logged).
• No non-english keyboard support
• I'm not including all symbols right now

[amwatson]

oh, additonally:

1. when the UI closes, the menu bar is still active, so users will have to close that. this will probably annoy people
2. the upside of doing the keyboard this way is that users should be able to use external keyboards if they want to