add support for update_raw_description() to *add* a decsription to a node;
add support for update_raw_description() to *add* a decsription to a node;

BenGardiner/mindmup-as-attack-trees,BenGardiner/mindmup-as-attack-trees,BenGardiner/mindmup-as-attack-trees,BenGardiner/mindmup-as-attack-trees