Reworked trade window

[akortunov]

1. Use AutoSizedTextBox instead of TextBox (should fix the trade window issue from bug #4215).
2. Increased minimum window width to handle more long labels (have we a better solution? Ideally, buttons should not overlap each others.)
3. Every line is wrapped to the HBox, so PlayerGold and MerchantGold can use a "Right" alignment.

[ghost]

Can we not increase the width of the number edit box? It's already hideously wide as it is. If at all, the width should match the english label which is what most players would see.Looks like your PR didn't make the edit box wider. I could swear it was smaller before. Maybe it should be, anyway...

I tested some alternate layouts to use that extra horizontal space for the +/- buttons, but I don't really like them. The first one is too hard to click on and the other ones you have to move your mouse more to go from + to -.

[akortunov]

I thought about alternative layouts too:

But text labels may have different length on different languages.

[akortunov]

Or something like:

[ghost]

The last one is quite nice. Actually using '>>' for 'Max Sale' would solve an issue with the german version (or all localised versions?) where they forgot to translate the label.

But the one thing I don't like about it is how the '+' and '-' don't match up vertically. I guess that can't be fixed as it's a problem with the font.

[mychaelo]

But the one thing I don't like about it is how the '+' and '-' don't match up vertically. I guess that can't be fixed as it's a problem with the font.

@scrawl Depends on which character was used. The usual 'fake minus' hyphen is not supposed to be lined up with the plus, but the U+2212 code point 'MINUS SIGN' must do so.

See Wiki pic for comparison: https://en.wikipedia.org/wiki/File:Plus_Minus_Hyphen-minus.svg

[akortunov]

but the U+2212 code point 'MINUS SIGN' must do so.

I tried to use this character previously, but OpenMW does not support it (? is displayed).
I do not know if there is an issue on the engine side, or on the font side.