CLI error message could be more specific

_From [marisa.d...@gmail.com](https://code.google.com/u/115886856648841171353/) on June 27, 2013 21:28:44_

From a user:

"I did get the nimas validator to work and it looks promising. The biggest problem we are going to have with it is that it is very easy to make it fail for simple reasons, like a typo in a path or something, and it doesn't give any good feedback. All you get on the console is the "Usage" message. So, you know that it didn't like one of the arguments but there's no hint as to which one it didn't like."

Suggestion:

Give specific feedback about which script parameter was incorrect.

_Original issue: http://code.google.com/p/daisy-pipeline/issues/detail?id=337_