Support Non-American Keyboards

[Firionus]

Currently, the plan is to use the Hotkey-support built into Blueprint.js. However, their implementation currently is only valid for US keyboards. For example, the hotkey help dialog should be opened by "?", but on a german keyboard " ' " must be pressed.

Please track palantir/blueprint#4165 for resolving this problem. Alternatively, we can for example consider changing back to react-hotkeys-hook or go to mousetrap/hotkeys libraries directly.