Change decimal/thousands separator based on locale

[EvanHahn]

In English, I might write 4,206.9. In Spanish, I might write 4.206,9.

You should be able to override this, but we'll need to add this to the language definitions.

Some related links I found:

• https://en.wikipedia.org/wiki/Decimal_mark#Hindu.E2.80.93Arabic_numeral_system
• https://docs.oracle.com/cd/E19455-01/806-0169/overview-9/index.html