actuators/universal_robots: added optional fields (e.g., acceleration, speed, etc) to input stream
actuators/universal_robots: improved help in ur-arm-command.cpp
actuators/universal_robots: renamed robot_mode -> mode
actuators/universal_robots: using joint_values type (with joint names as fields) instead of arrays
actuators/universal_robots: simplified packed_joint_values_t and moved packed structures to base.h