add description to fri state msg

kuka_driver_interfaces/msg/FRIState.msg

@@ -1,11 +1,39 @@
 # Message describing the state of the robot and FRI
 
+# FRI session state enum 
+# IDLE = 0, MONITORING_WAIT = 1, MONITORING_READY = 2,COMMANDING_WAIT = 3, COMMANDING_ACTIVE = 4
 int32 session_state
+
+# FRI connection quality
+# POOR = 0, FAIR = 1, GOOD = 2, EXCELLENT = 3
 int32 connection_quality
+
+# Safety state
+# NORMAL_OPERATION = 0, SAFETY_STOP_LEVEL_0 = 1, SAFETY_STOP_LEVEL_1 = 2, SAFETY_STOP_LEVEL_2 = 3
 int32 safety_state
+
+# Client command mode
+# NO_COMMAND_MODE = 0, POSITION = 1, WRENCH = 2, TORQUE = 3
 int32 command_mode
+
+# Control mode of the robot
+# POSITION_CONTROL_MODE = 0, CART_IMP_CONTROL_MODE = 1, JOINT_IMP_CONTROL_MODE = 2, NO_CONTROL = 3
 int32 control_mode
+
+# Operation mode
+# TEST_MODE_1 = 0, TEST_MODE_2 = 1, AUTOMATIC_MODE = 2
 int32 operation_mode
+
+# Drive state
+# OFF = 0, TRANSITIONING = 1, ACTIVE = 2
 int32 drive_state
+
+# Overlay overlay_type
+# NO_OVERLAY = 0, JOINT = 1, CARTESIAN = 2
 int32 overlay_type
+
+# Tracking performance of the robot
+# Indicates how well the commanded robot is able to follow the commands of the FRI client.
+# The best possible value is 1.0, when the robot executes the given commands instantaneously.
+# The tracking performance is always 0 when the session state is not COMMANDING_ACTIVE.
 float64 tracking_performance