Add locale parameter for numberFormat

Use case

When mapping from BigDecimal / double to String type (maybe like a number with 2 digits after separator), then it choose separator with honor to default program locale.
So, the results is incosistent. On my computer i have a locale with "ru/RU" and it choose ',' as separator, but on remote tests with locale "en/US" it chooses '.'

Generated Code

Add a locale parameter with conjuction to numberFormat

Possible workarounds

Workaround - have a separate util method with manually created DecimalFormat.

MapStruct Version

MapStruct 1.5.5.Final