support multi-line description

[jchip]

allow description to be an array of strings, or strings with \n, and display it in multi-lines?

[chmontgomery]

Seems like a good change. I accept PRs

[jchip]

Actually you can already put \n in the help message, but it would come out without indents.
Is this change reasonable to you?
jchip@813d566

[chmontgomery]

Thanks! I hope to test this out shortly and let you know.