Add string formatting options to ToQuanity

[dealdiane]

Would be nice to add a string format parameter to ToQuantity.

"woman".ToQuantity(12345, "N0") would return "12,345 women". End users prefer to see numbers in a more familiar way.

[dealdiane]

can't figure out how github works but I forked it and made this commit. Formatting option is only available when showQuantityAs = ShowQuantityAs.Numeric. Format parameter doesn't make sense if the number is converted to words.

dealdiane@6fd29d5

[MehdiK]

Nice. I like it. Please create a Pull Request for it. Here is a guide.

Please also write unit tests for it and also add your PR to the release-notes file. Thanks.

[MehdiK]

This was done in #220.