Allow input via hardware keyboard

[yawnoc]

Feature request from Day Day Run on Google Play:

可以用係有實體鍵盤嘅電話？即係唔洗係個mon到篤

Or:

Can [it be] used on phones that have a hardware keyboard? i.e. not having to poke on the screen

[yawnoc]

This seems feasible (just need to override InputMethodService.onKeyDown etc.).

Hardware key logic can probably follow the JavaScript port (minus logic for things like tone markers, which the average user won't use).

Changing the appearance of the soft keyboard when a hardware keyboard is present will probably be too hard though.