oiiotool --nosoftwareattrib suppresses the altering of Software & ImageHistory
fields upon output.
Tighten up error propagation through IC, IB, and oiiotool.

Now we get nice helpful error messages if any of the input images are
corrupt or incomplete.
More tightening up of error reporting for oiiotool.

Found all places that haphazardly wrote error messages or warnings to
cerr or cout, and replaced them with legit error() or warning() calls
so that they all behave the same way including proper exit of oiiotool
with the right return code.