Allow negative default values

dynamixel/model/h42_20_s300_r.py

dynamixel/model/h42_20_s300_r_a.py

dynamixel/model/h54_100_s500_r.py

dynamixel/model/h54_100_s500_r_a.py

dynamixel/model/h54_200_s500_r.py

dynamixel/model/h54_200_s500_r_a.py

dynamixel/model/l42_10_s300_r.py

dynamixel/model/l54_30_s400_r.py

dynamixel/model/l54_30_s500_r.py

dynamixel/model/l54_50_s290_r.py

dynamixel/model/l54_50_s500_r.py

dynamixel/model/m42_10_s260_r.py

dynamixel/model/m42_10_s260_r_a.py

dynamixel/model/m54_40_s250_r.py

dynamixel/model/m54_40_s250_r_a.py

dynamixel/model/m54_60_s250_r.py

dynamixel/model/m54_60_s250_r_a.py

dynamixel/model/ph42_020_s300_r.py

dynamixel/model/ph54_100_s500_r.py

dynamixel/model/ph54_200_s500_r.py