add node::SetValue(DataValue &) for finer grained control of write api
new signature SetValue(const Variant& val, const DateTime& = CurrentDateTime())

refer to issue #56 for discussion
Merge pull request #65 from oroulet/master

handle and use ServiceFault, bugfix
Merge pull request #64 from mdcb-gmt/master

DateTime argument to Node::SetValue, Node::SetAttribute
Clean output