Added fog emitter event

[nkoenig]

Adds region events to fog emitters.

To test:

1. ign launch cloudsim_sim.ign worldName:=finals_practice_01 circuit:=finals robotName1:=X1 robotConfig1:=X1_SENSOR_CONFIG_1 ros:=true durationSec:=3600
2. Follow the robot in the GUI.
3. rostopic echo /subt/region_event
4. tail -f /tmp/ign/logs/gazebo/events.yml
5. ign service -s /world/finals_practice_01/set_pose /set_pose --reqtype ignition.msgs.Pose --reptype ignition.msgs.Boolean --timeout 300 --req 'name: "X1", position {x:20 y:-40 z:0.5}'

After step 5 you should see:

From the rostopic echo:

---
timestamp: 
  secs: 16
  nsecs: 496000000
event_type: "fog"
robot_name: ''
detector: "fog_emitter_1"
state: "fog"
event_id: 4

In /tmp/ign/logs/gazebo/events.yml

- event:
  id: 4
  type: fog
  time_sec: 16
  model: fog_emitter_1

Signed-off-by: Nate Koenig [email protected]

[mjcarroll]

Looks good and works for me 👍