expose quiet flag in class InputGroup

[matthewweippert]

The InputGroup class has a private member "quiet" which will disable print statements while reading parameters from the file. However, there is no way to set or modifiy this flag.

I propose adding quiet as an optional parameter to the InputGroup constructors. If this were set to false, then the default behavoir should be unchanged.

If this could be done in the v2 branch that would be helpful.