Added AddObject method to node object using new AddNodes. It compiles but does nothing yet
small improvements in add_object
Merge pull request #2 from treww/master

Throwing only Common::Error.
Merge branch 'master' of https://github.com/FreeOpcUa/opcua-core
use new node_management header
port Node to AddNodes method. working
Merge pull request #3 from oroulet/master

adapt to new node_management header, port Node to AddNodes
Little refactoring with errors and converting objects to strings.