minor change
Merge branch 'external_datasource' of https://github.com/acplt/open62541 into external_datasource
addNodes, addReferences divided
changes to the interface: addReferencesEntry/addReferencesInverseEntry
added addNodes for client (for tests only)
workaround for encoding an extension object (done manually)
added client functionality to add a node to ns0
turned off the check "nodes to ns0 not allowed over wire"
Merge branch 'external_datasource' of https://github.com/acplt/open62541 into external_datasource

Conflicts:
	include/ua_server.h
	src/server/ua_services_attribute.c
	src/server/ua_services_nodemanagement.c
	src/ua_types_encoding_binary.c