Make gui tooltips referring to key assignments dynamic

That is, make them not lie when keys are reconfigured.

This did use our key names **verbose**, so some of it was rather awkward: `+-,.` were spelled out, so was `Esc`.
That looked like this:

```
Rotate map clockwise (Period)
Decrease game speed (Minus)
Build menu (B)
Game menu (Escape)
Rotate map counterclockwise (Comma)
Captain's log (L)
Increase game speed (Plus)
Destroy (X)
```
For now, we manually replace the longer key names in constants. Thus,

```
Rotate map clockwise (+)
Decrease game speed (-)
...
```