made all usage of command util exception functions mark with throw

CommonUtil exception methods now "return" the exception so Java's dead-code checker can find dead code.  Updated all the code to "throw" the return.  This patch doesn't change any real logic, its more of relying on java's dead code checker.


Also, the functions can be replaced by functions in guava.  Would it be good to remove this code and replace it with guava's?  If thats ok, I can update the patch to do that.
The original implementation just helper method to throw IllegalArgumentException. 
The patch makes it useful by allowing throw exception returned by calling method illegalArgumentException() which could wrap the original msg with some additional error message.