TAKE ONE maximality implemented
implement TAKE ONE and TAKE MANY

fix bugs

fix bugs
fix bugs
fix bugs

fix bugs for bis step maximality

fix bugs for bis step maximality

fix bugs for bis step maximality
start use git ignore
more test
use gitignore
change gitignore
implement syntactic maximality
change gitignore place
add constraint that a sm can have only one region
add BSMLHelper class
add BSMLHelper class
change ignore file
change varialbe reference machanism; add snapshot_big_step
implement memory protocol
change git ignore
change git ignore
fix bugs
fix bugs for getArena()