Fix spacing between numbers and units of measure

[sikmir]

With regards to typography, English style guides say:

• percent (%) and degree (°) signs follow the number without any space
• all other units of measure (mm, min, etc.) — with space

I think the same rules should apply for UI output, but it's discussable.

TODO: other languages have other rules at least for spacing in front of the percent sign, so ideally it should be moved to translations.

Examples (before): Examples (after):

[dg0yt]

Looks to me like this really needs to be addressed in translation. OTOH there is no need to hurry.

[dg0yt]

From the Wikipedia links, I see that we do not only have to deal with the space, but also with suffix vs. prefix:

• English: 5%
• German: 5 %
• Turkish: %5

To handle this in translation, we could use Unit::tr("5%"). The translator would see "5%" and use the proper style (e.g. "5 %"). The calling function would need to lookup the location of '5' and then set prefix and suffix (spinbox), or replace '5' with the actual number for normal output.