changed the overwriting method of contact when the object falled down.
changed the variable name of arrow.
make eusmodels for each gazebo model in init function.
deleted unneccesary comment lines
deal with each model at a same time in the function for updating coord and contact during manipulation
update all arrow in manip
changed variable name
add option for setting update-flag in update-coord/contact function
save and check the states of each object