fix missing try block in CIMIndicationListener::start()
introduce Python3 compatibility

By default, LMIWBEM is configured to use Python2.
introduce WBEMConnection::creds
rename WBEMConnection(verify_server_cert) to no_verification
do not pass properties, qualifiers and keybindings by reference

Properties, qualifiers and keybindings are copied, when creating CIMInstance or CIMInstanceName
introduce type checks for NocaseDict::update()
fix WBEMConnection::createInstance() when no object path is available
introduce type recognition in CIMInstanceName::keybindings
add missing getters for CIMClass properties
introduce lmiwbem.is_subclass()
fix CIMIndicationListener::start() boost::python parameters passing
switch CIMIndicationListener::is_alive() to property