Provided by @gerhaher: removed some duplicated keys, replaced
them with other useful ones (to swedish and kenyan people).
Stick cyrillic letter io to a single key
French keyboard: aligned to std.lua, fixed '.' and ',' keys.
* Add a basic Japanese keyboard layout
Allow for entring Japanese text into text boxes. Only supports kana
and latin letters due to limitations of current VirtualKeyboard
implementation (complex text input with conversion is not possible).
* Allow keyboard layouts to declare custom modifiers
Refactor modifier key setup code and existing keyboard layouts so
that each layout can declare custom modifier key labels. This
allows for greater extensibility and for future keyboard layouts.
