fix a bug found by coverity
adjust unit test to datetime print
export functions to add nodes in the server
add attribute-types to add nodes to minimal node set
simplified adding of scalar nodes from userland
add example to the readme
implemnted CloseSecureChannel request handlig, started to work on handling CLoseSessionRequest, relates to #129
remove pointers to securechannel when the connection closes, see #128
implemented handling CloseSessionRequests, no error message by UaExpert anymore, relates to #129