Show logical labels for keyboard keys

[wjt]

The keyboard bindings for our input actions are bound to "Physical Keycode (Position on US QWERTY Keyboard)". This means that regardless of the keyboard layout in use, pressing the keys in the same physical position as WASD on a US English keyboard moves the player; X throws; Z repels; etc.

On a French AZERTY keyboard the glyphs printed on these keys are different. QWERTZ (used chiefly in German-speaking countries) also has one relevant difference. (Keyboards with Dvorak labels are even rarer than Dvorak typists and I don't think we should go out of our way to support Dvorak users unless it also helps us support AZERTY and other regional layouts that normal people use, but since I do actually type Dvorak I can use myself as a proxy for an AZERTY user so I include Dvorak in the table below :))

Action	QWERTY	QWERTZ	AZERTY	Dvorak
Up	W	W	Z	,
Left	A	A	Q	A
Down	S	S	S	O
Right	D	D	D	E
Throw	X	X	X	Q
Repel	Z	Y	C	J

I think it is the correct behaviour to bind the physical location rather than the logical key symbols; but we currently show QWERTY labels to the player too:

(We don't show WASD anywhere, but annoyingly Z to repel is one of the keys that really is differently labelled on the two major non-QWERTY Latin layouts.)

I think we should adjust the displayed symbols to reflect the logical value of the key rather than showing the QWERTY one.

[wjt]

This is relevant to the demo because at Serious Play Europe in Mainz (Germany) Threadbare will be exhibited on a laptop with an AZERTY (French) keyboard.

[wjt]

I think we can do this quite nicely with yet another change to how the textures are stored.

Right now what we store is, for each device type, a mapping between input action and texture.

Instead we should have a mapping from e.g. "joypad button 1" to texture, then map the event to its joypad button number. The Input Helper addon has some logic for this already.