fix #include
overload Node::SetValue, add optional datetime=Current
add Node::SetDataValue
add DateTime class wrapper
add CurrentDateTime, ToDateTime, ToTimeT function wrappers
add DataValueWrap and matching wrapper
FIXME: PyDataValue and DataValue left as they stand, needs cleanup
fix indent
Merge pull request #19 from mdcb-gmt/master

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