Handle "infinite" attacker potentials properly
Handle "infinite" attacker potentials properly

By using string forms in JSON and converting back to float forms for
Python. Previous version would insert a 309 digit "max float" value into
JSON and would ruin table output.

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